Cannot install add-ons because of connection error
No add-ons coming from https://addons.mozilla.org/en-US/firefox/ can be installed in my Mac, all because of a single issue ("Download failed. Please check your connection."). I've noticed that images in this site cannot load properly as well. I checked the console and it seems that the GET request was responded with 404. Install requests sent to other websites seem to be working. I successfully installed zotero from its website and some other add-ons via downloaded .xpi files. However, some .xpi's cannot be installed directly either. I got a message saying this add-on appears to be corrupt.
I duckduckwent this issue and tried all the following solutions (though none has helped): 1. Added "xpinstall.enabled => true" and "xpinstall.signatures.required => false" in about:config; 2. Downloaded the .xpi file directly using other browsers, but when I tried to add it manually, I got the message saying this add-on is corrupt. 3. I tried InstallTrigger.install({URL: "https://addons.mozilla.org/firefox/downloads/file/1168281/adblock_plus-3.4.2-an+fx.xpi?src=search"}) in the console and still got the connection error. I clicked on several install links in add-ons websites and they came back with 404. I think these links were redirecting me to addons.mozilla.org.
I don't have any antivirus software in my Mac, at least not that I know of. I enabled "allow site to install add-ons" and "allow pop-ups", etc.
Chosen solution
yc_cxy said
jscher2000 saidI wonder why you do not get that redirect? Are you using a proxy of any kind?It rings a bell – I do have "Cisco AnyConnect Secure Mobility Client" installed but use its VPN service only very infrequently to the extent that I forget I have this application in my Mac in the first place.
That is the only proxy I use as far as I know but it's closed for the most part. Could it be possibly the cause?
Hmm, does it make any difference if you use it?
Probably your connection setting is the default, but you can check here:
- Windows: "3-bar" menu button (or Tools menu) > Options
- Mac: "3-bar" menu button (or Firefox menu) > Preferences
- Linux: "3-bar" menu button (or Edit menu) > Preferences
- Any system: type or paste about:preferences into the address bar and press Enter/Return to load it
In the search box at the top of the page, type proxy and Firefox should filter to the "Settings" button, which you can click.
I believe the default is "Use system proxy settings", which piggybacks on your Windows/IE "LAN" setting. "Auto-detect" can lead to a flaky connection. I'm not sure "No proxy" would be compatible with your Cisco VPN client, but you could test whether it makes any difference.
Anything odd here?
Read this answer in context 👍 0All Replies (20)
A 404 is a server communication issue. How was your firefox upgraded or installed?
WestEnd said
How was your firefox upgraded or installed?
Hi WestEnd. I am using a Mac so I downloaded the app from mozilla.org and dragged it into my Applications folder. Currently, I am on Firefox Quantum 64.0.
Modified by yc_cxy
I am really curious about why requests sent to https://addons.mozilla.org/en-US/firefox/ are being responded with 404. Happy new year folks.
Hi yc_cxy, in your screenshot, the icon for ABP that normally appears above the name is not loading. The image URL is
https://addons.cdn.mozilla.net/user-media/addon_icons/1/1865-64.png?modified=mcrushed
Does your Firefox load that?
I ask because that server is important:
When I click the install button for ABP, Firefox requests
The server sends a redirect to
So you need that server to be accessible.
Hello, jscher2000
jscher2000 said
Does your Firefox load that?
Nope. I have actually tried accessing those redirect links before and all of them came back with 404. This happens not only to ABP but also other add-ons. In fact, no image loads properly in https://addons.mozilla.org/en-US/firefox/.
My guess is that all requests are sent to a common server. I tried sending requests using Postman but it did not quite work out.
Do you have enabled TRR (DNS-over-HTTPS)? You can check this pref on the about:config page: network.trr.mode = 0
You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.
Try to disable IPv6 (check for other possible causes as well).
Modified by cor-el
yc_cxy said
My guess is that all requests are sent to a common server. I tried sending requests using Postman but it did not quite work out.
I don't know what Postman is... Are you are blocked from loading content off of addons.cdn.mozilla.net in other browsers, or only Firefox?
jscher2000 said
Are you are blocked from loading content off of addons.cdn.mozilla.net in other browsers, or only Firefox?
Not just firefox. It also shows up as 404 in other browsers (safari and google chrome).
cor-el said
Do you have enabled TRR (DNS-over-HTTPS)? You can check this pref on the about:config page: network.trr.mode = 0
Yes.
I have disabled both IPv6 and DNS Prefetching but it does not seem to work.....
yc_cxy said
jscher2000 saidAre you are blocked from loading content off of addons.cdn.mozilla.net in other browsers, or only Firefox?Not just firefox. It also shows up as 404 in other browsers (safari and google chrome).
Okay, let's assume it is something "upstream" from your browsers. Do you use any parental control filters? Do you use any security sofware filters that may not like "cdn" addresses?
Also, in case your router has gone haywire, you could "power cycle" it: disconnect from power for 10 seconds, then reconnect.
jscher2000 said
Do you use any parental control filters? Do you use any security sofware filters that may not like "cdn" addresses?
I don't really use any parental control or security software. Firewall is always off in my Mac.
Also, in case your router has gone haywire, you could "power cycle" it: disconnect from power for 10 seconds, then reconnect.
I was using a school wi-fi for the most part and don't really have access to the router. Currently, I am on break at home and have just tested that out on my home router. However, the issue persists.
Update. I posted this issue in some other platform and got the following answer.
You are using Verizon as ISP or somewhere in the proxy chain between your laptop and our servers, and it is a Verizon proxy server that replies with a 404 for some reasons, not mozilla servers. The answer to "why does Verizon return a 404?" is a mystery though, but the fact that you cannot download the file with another browser makes me think that the problem is related to your Internet connection. You should try to install an add-on from another Internet connection.
It seems to make a lot of sense but as I try to install add-ons using other internet connections, the problem persists.
jscher2000 said
Hi yc_cxy, in your screenshot, the icon for ABP that normally appears above the name is not loading. The image URL is https://addons.cdn.mozilla.net/user-media/addon_icons/1/1865-64.png?modified=mcrushed Does your Firefox load that? I ask because that server is important: When I click the install button for ABP, Firefox requests https://addons.mozilla.org/firefox/downloads/file/1168281/adblock_plus-3.4.2-an+fx.xpi?src=dp-btn-primary The server sends a redirect to https://addons.cdn.mozilla.net/user-media/addons/1865/adblock_plus-3.4.2-an+fx.xpi?filehash=sha256:323dfd642bef52784df6e5f495d8d0a4d8fad19cd470bef7417d13dea9a95f8f So you need that server to be accessible.
It turns out that these redirect links could not be opened in my computer no matter what browser or internet connect I use. It responds with the "Potential Security Issue" (see screenshot attached).
It's asking me if my computer is set to the correct timezone, which it is but the problem persists.
Also,
yc_cxy said
Update. I posted this issue in some other platform and got the following answer.You are using Verizon as ISP or somewhere in the proxy chain between your laptop and our servers, and it is a Verizon proxy server that replies with a 404 for some reasons, not mozilla servers. The answer to "why does Verizon return a 404?" is a mystery though, but the fact that you cannot download the file with another browser makes me think that the problem is related to your Internet connection. You should try to install an add-on from another Internet connection.
It does not solve this issue no matter what internet connection I use. I start to think that there is something wrong with local settings in my laptop.
yc_cxy said
It turns out that these redirect links could not be opened in my computer no matter what browser or internet connect I use. It responds with the "Potential Security Issue" (see screenshot attached). It's asking me if my computer is set to the correct timezone, which it is but the problem persists.
Hmm, all browsers. Possibly an external filter issue, such as security software or in the router? If it wouldn't cause cries of anguish in your house, have you tried power-cycling your router (for example, unplug, wait 10 seconds, plug back in)?
Also, in the screenshot, if you click the "More Information" button, what information do you find there? Sometimes there is a link to click to view the problem certificate which can provide clues about an intermediary. If the certificate is encoded (block of gibberish) you can use a site like the following to decode it:
jscher2000 said
Possibly an external filter issue, such as security software or in the router? If it wouldn't cause cries of anguish in your house, have you tried power-cycling your router (for example, unplug, wait 10 seconds, plug back in)?
I did try power-cycling but it does not seem to work. I think it's something in my mac instead of the router or specific internet connection as I've tried switching multiple wifi connections. However, I am not using any security software so I am confused where else could it come from.
Also, in the screenshot, if you click the "More Information" button, what information do you find there? Sometimes there is a link to click to view the problem certificate which can provide clues about an intermediary.
Please see the attached screenshot for this. It shows a certificate that expires on Jan 16th, 2019 and time zone in my laptop is correctly set. So that does make the certificate expire in this case but why does *.cdn.mozilla.net has a certificate that expires on Jan 16th, 2019?
Modified by yc_cxy
Good question, where is that old certificate coming from? Could you check the Certificate Manager:
- Mac: "3-bar" menu button (or Firefox menu) > Preferences
- Windows: "3-bar" menu button (or Tools menu) > Options
- Linux: "3-bar" menu button (or Edit menu) > Preferences
- Any system: type or paste about:preferences into the address bar and press Enter/Return to load it
In the search box at the top of the page, type cert and Firefox should filter to the "Certificates" section, where you can click the "View Certificates" button.
In the Certificate Manager dialog, try the "Servers" list. Firefox includes a couple DigiNotar entries. Do you see anything related to the problem certificate that you could remove?
I guess you could also check the Mac keychain, since Safari and Chrome use that. (I don't know the steps, however.)
jscher2000 said
Good question, where is that old certificate coming from? Could you check the Certificate Manager:
I checked the certificates but did not see anything unusual or the expired certificate I saw in the warning page.
Modified by yc_cxy
The main issue seems to be that I cannot access addons.cdn.mozilla.net or related web address. I am thinking maybe there is something in my mac that is blocking a cdn or something else in the URL.
However, I am not using any antivirus software and my firewall is off. I am quite confused at this point.
You can check if there is more detail available about the issuer of the certificate.
- click the "Advanced" button show more details
- click the blue error text (SEC_ERROR_UNKNOWN_ISSUER) to show the certificate chain
- click "Copy text to clipboard" and paste the base64 certificate chain text in a reply
If clicking the blue error text doesn't provide the certificate chain then try these steps to inspect the certificate.
- open the Servers tab in the Certificate Manager
- Options/Preferences -> Privacy & Security
Certificates: View Certificates -> Servers: "Add Exception"
- Options/Preferences -> Privacy & Security
- paste the URL of the website (https://xxx.xxx) in it's Location field
Let Firefox retrieve the certificate -> "Get Certificate"
- click the "View" button and inspect the certificate
You can find detail like the issuer of the certificate and intermediate certificates in the Details tab.
cor-el said
You can check if there is more detail available about the issuer of the certificate.
- click "Copy text to clipboard" and paste the base64 certificate chain text in a reply
Here you go:
Peer’s Certificate has expired.
HTTP Strict Transport Security: false HTTP Public Key Pinning: true
Certificate chain:
BEGIN CERTIFICATE-----
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END CERTIFICATE-----
BEGIN CERTIFICATE-----
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END CERTIFICATE-----