Hello,

The error "NS_ERROR_UNKNOWN_HOST" tends to suggest that your DNS cache needs to be flushed.

While I do not use MacOS, the common consensus of a search states that the command sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder should do it, but you should do your research before executing that, as I do not use MacOS.

Those error logs are on my Windows PC - where ALL my bookmarks and stuff I WANT synced are.

I popped into PowerShell (as Admin) and flushed the DNS cache. Hopefully it'll work... but this has been done before b/c I thought that might be a problem... though it's odd to me that ONLY Firefox's sync thing was having this problem.

FWIW though... Mobile Firefox won't sync up either. Zapping the QR code just gives a white screen with NOTHING ever happening until I back out of the setting to sync. And logging in manually doesn't show ANY bookmarks from the desktop. For whatever reason Firefox is NOT sending the sync information from my Win10 PC TO the sync servers- it's just NOT connecting.

While I am not sure I can help with mobile, as I do not use Firefox mobile,

You can manually move the profile between the computers, the instructions to do so can be found at Back up and restore information in Firefox profiles

I do not understand why the sync is not working, but this should at least form a stopgap solution.

Can you resolve sync-1-us-west1-g.sync.services.mozilla.com in the DNS Lookup tool if you visit about:networking via the address bar ?

While I am not sure I can help with mobile, as I do not use Firefox mobile, You can manually move the profile between the computers, the instructions to do so can be found at Back up and restore information in Firefox profiles I do not understand why the sync is not working, but this should at least form a stopgap solution.

This is such a late 1990's solution to have to pursue though. I did wind up doing this, but it's a pain in the butt work-around for something that should work without needing to copy 500MB of data around manually and editing the profiles.ini file by hand. It's really not a solution to the problem- and if I wasn't a computer nerd kind of person, I wouldn't have ANY CLUE how to find the buried in the system structure profile data or know where to put it on a different OS, and how to change the ini to launch it properly.

For such a push on this mozilla account thing and sync'ing things between devices, it REALLY just needs to WORK on at least the most fundamental things like bookmarks.

Can you resolve sync-1-us-west1-g.sync.services.mozilla.com in the DNS Lookup tool if you visit about:networking via the address bar ?

The "resolve" button does literally nothing at all when I click on it. No matter what address I put in there to resolve. It turns darker grey when I click on it, and back to the light grey when I let go of the mouse button. But NOTHING happens, at all. Literally doesn't even try to do anything. Not an error as in it can't resolve, just literally NOTHING happens.

Yet it clearly DOES have DNS resolving as I can surf just fine with it. I can get to websites and watch videos, play games, etc.

An addendum- this happens on EVERY profile. I even created one with literally NOTHING on it, brand new... and it has the exact same behavior.

And the latest Sync logs show nothing but FF failing to sync...

1715025862860 Sync.SyncScheduler DEBUG Next sync in 3600000 ms. (why=schedule) 1715025866289 Sync.SyncScheduler DEBUG Network link status changed to "changed". Offline?: false 1715025866367 Sync.SyncScheduler DEBUG Network link status changed to "down". Offline?: false 1715025866367 Sync.SyncScheduler DEBUG Clearing sync triggers and the global score. 1715025866368 Sync.SyncScheduler DEBUG Next sync in 3600000 ms. (why=schedule) 1715032561478 Sync.SyncScheduler DEBUG Woke from sleep. 1715032562742 Sync.SyncScheduler DEBUG Network link status changed to "up". Offline?: false 1715032562742 Sync.SyncScheduler DEBUG Network link looks up. Syncing. 1715032562755 Sync.SyncScheduler DEBUG Network link status changed to "changed". Offline?: false 1715032562799 Sync.SyncScheduler DEBUG Network link status changed to "changed". Offline?: false 1715032562837 Sync.Service DEBUG User-Agent: Firefox/125.0.3 (Windows NT 10.0; Win64; x64) FxSync/1.127.0.20240425211020.desktop 1715032562837 Sync.Service INFO Starting sync at 2024-05-06 16:56:02 in browser session cib26wOTSy6t 1715032562837 Sync.SyncScheduler DEBUG Clearing sync triggers and the global score. 1715032562839 Sync.Status INFO Resetting Status. 1715032562839 Sync.Status DEBUG Status.service: success.status_ok => success.status_ok 1715032562839 FirefoxAccounts DEBUG FxAccountsProfileClient: Requested profile 1715032562839 FirefoxAccounts DEBUG getOAuthToken enter 1715032562839 FirefoxAccounts TRACE getCachedToken returning cached token 1715032562839 FirefoxAccounts DEBUG getOAuthToken returning a cached token 1715032562840 Services.Common.RESTRequest DEBUG GET request to https://profile.accounts.firefox.com/v1/profile 1715032562840 Sync.SyncAuthManager INFO Getting sync key 1715032562840 FirefoxAccounts DEBUG getOAuthToken enter 1715032562840 FirefoxAccounts TRACE getCachedToken returning cached token 1715032562840 FirefoxAccounts DEBUG getOAuthToken returning a cached token 1715032562840 Sync.SyncAuthManager INFO Getting a sync token from: https://token.services.mozilla.com/1.0/sync/1.5 1715032562840 Sync.SyncAuthManager DEBUG Getting a token using OAuth 1715032562840 Services.Common.TokenServerClient DEBUG Beginning OAuth token exchange: https://token.services.mozilla.com/1.0/sync/1.5 1715032562840 Services.Common.RESTRequest DEBUG GET request to https://token.services.mozilla.com/1.0/sync/1.5 1715032563080 Services.Common.RESTRequest DEBUG GET https://profile.accounts.firefox.com/v1/profile failed: 2152398878 - NS_ERROR_UNKNOWN_HOST 1715032563080 FirefoxAccounts ERROR Background refresh of profile failed: {"name":"FxAccountsProfileClientError","code":null,"errno":998,"error":"NETWORK_ERROR","message":"[Exception... \"NS_ERROR_UNKNOWN_HOST\" nsresult: \"0x804b001e (NS_ERROR_UNKNOWN_HOST)\" location: \"JS frame :: resource://services-common/rest.sys.mjs :: onStopRequest :: line 478\" data: no]"} 1715032563095 Services.Common.RESTRequest DEBUG GET https://token.services.mozilla.com/1.0/sync/1.5 failed: 2152398878 - NS_ERROR_UNKNOWN_HOST 1715032563095 Sync.SyncAuthManager ERROR Non-authentication error in _fetchTokenForUser: TokenServerClientNetworkError({"error":{}})(resource://services-common/tokenserverclient.sys.mjs:28:36) JS Stack trace: TokenServerClientNetworkError@tokenserverclient.sys.mjs:51:16 _tokenServerExchangeRequest@tokenserverclient.sys.mjs:235:13 1715032563096 Sync.Status DEBUG Status.login: success.login => error.login.reason.network 1715032563096 Sync.Status DEBUG Status.service: success.status_ok => error.login.failed 1715032563096 Sync.SyncAuthManager ERROR Failed to fetch a token for authentication: TokenServerClientNetworkError({"error":{}})(resource://services-common/tokenserverclient.sys.mjs:28:36) JS Stack trace: TokenServerClientNetworkError@tokenserverclient.sys.mjs:51:16 _tokenServerExchangeRequest@tokenserverclient.sys.mjs:235:13 1715032563096 FirefoxAccounts TRACE not checking freshness of profile as it remains recent 1715032563166 Sync.Resource WARN GET request to https://sync-1-us-west1-g.sync.services.mozilla.com/1.5/209631697/info/collections failed: [Exception... "The lookup of the hostname failed" nsresult: "0x804b001e (NS_ERROR_UNKNOWN_HOST)" location: "<unknown>" data: no] No traceback available 1715032563166 Sync.Status DEBUG Status.sync: success.sync => error.login.reason.network 1715032563167 Sync.Status DEBUG Status.service: error.login.failed => error.sync.failed 1715032563167 Sync.ErrorHandler ERROR Sync encountered an error: [Exception... "The lookup of the hostname failed" nsresult: "0x804b001e (NS_ERROR_UNKNOWN_HOST)" location: "<unknown>" data: no] No traceback available 1715032563167 Sync.SyncScheduler DEBUG Next sync in 3600000 ms. (why=reschedule) 1715032563167 Sync.Telemetry INFO Early submission of sync telemetry due to changed IDs/NodeType 1715032563169 Sync.Service DEBUG Exception calling anonymous function: [Exception... "The lookup of the hostname failed" nsresult: "0x804b001e (NS_ERROR_UNKNOWN_HOST)" location: "<unknown>" data: no] No traceback available

Something is fundamentally broken here. I just can't figure out what, or why.

What do you see here ? see screenshot Also, post a screenshot so that we can see if the devices are seeing each other.

Do you use any NordVPN software?

What do you see here ? see screenshot Also, post a screenshot so that we can see if the devices are seeing each other.

The synced tabs just has a button to go to sync settings. In the settings, it does show both the PC and the Mac Mini.

Do you use any NordVPN software?

Nope. I don't use any VPN. I know I probably SHOULD... but I don't.

The solution I wound up using, the miracle that worked... literally uninstalling Firefox entirely and redownloading and reinstalling it. Then I copied the SAME PROFILE folder data and ini files into place... and suddenly it's working.

I have no explanation and can't make sense of this at all. I downloaded it DIRECTLY from Mozilla BOTH TIMES... but it's gone through about 18-20 months of updates on the Windows PC since that initial install.

IDK Why that would cause a problem or how it could... but apparently a clean install and using the former profiles somehow seemed to have fixed it. ?????

Still confused, but grateful it's working. And ALL of it - I can send tabs between the Mac and PC even now... IDK how/why... but it works, so I am not going to question it. lol

Glad to hear, mark it as resolved and have a nice day.