Hey B.

I'm new to your issue, so can you could provide steps to replicate?

THANK-YOU! I so strongly don't want to go to Edge, i am disgusted by MS's tactics to try to push it on the public!

Same initial actions in FF v78 (64bit) vs. several releases since 78, including whatever is the latest release as of yesterday:

1. Click on the "Print this page" icon (added from "Customize" to the top bar, same following sequence of events occur if i click on a "Print" button on a web page) > Print Preview display comes up
2. Click "Print", the first selection on the menu bar horizontally across the top area of the window > MS Printer selections window/dialog box comes up.
3. Click on "Microsoft print to pdf" in the "Select Printer" area, then click on "Print" lower right of the same window > "Save Print Output As" window/box should come up.

Ever since FF78 sometimes it does not even display this box. With the most recent release this window acts like a time bomb - if you don't enter the directory and file name in time, usually a few seconds at best, it closes itself without saving anything. I am once again running FF78 and this does not happen; i can sit around with that window open all i want and it does not close itself.

Frankly, i don't want to send you on a Snipe hunt, for when i ran a search on print pdf problems in Firefox i came up with numerous results, none of which were the same as mine, but if you can, THANK-YOU!!!

I will provide any additional info i can-

Yeah, it works for me(see screenshot), so the error only happens when using MS print to pdf?

Do you have this issue when trying to print to a printer? I would also try to remove the device, reboot and let windows reinstall it. see screenshot You can also use that button to see all events to check the logs.

You can also uninstall and reinstall it using these steps. see screenshot

This issue has persisted ever since release 79. I would think that the programmer(s) could "simply" look at what changed from 78 to 79 and revert, but apparently not.

Well, that is thousands of lines of code. There is a tool called Mozregression (https://mozilla.github.io/mozregression/) which allows a tester to specify a last good and first bad version and download/test intermediate nightly releases to triangulate on the change that causes the issue. However, since my system doesn't have the problem, there's no point in me running it. Either you or someone else that suffers this problem would need to do it. High bandwidth and patience are both highly recommended.

I, once again, have to uninstall the latest release (i installed it, allowing an "upgrade", thinking that by now someone there would have fixed that which at least to me is a critical routine), and reinstall Version 78.0, since that one isn't f'd up.

Another option to consider is the Extended Support Release of Firefox 78, which has very limited changes (mostly just critical security patches), and will be maintained through next Summer when the new ESR replaces it. More info here: Switch to Firefox Extended Support Release (ESR) for personal use.

As best as i recall, i could send output to physical printers - but that is relying on an aging memory! I will have to try.

I will do as you advised and uninstall MS Print to pdf, pray it gets re-installed, and then install the latest upgrade-

Ummmmm, how do i get Windows to reload Print to pdf??? It is no longer available!

Edit: Oh, i forgot to mention - it prints fine to a physical printer, because in printing to a physical printer the "Save to" dialog box (or whatever it is called) isn't even used, and that is the one that kept getting closed...

Edit: FOund instructions on how to reinstall Print to pdf, hoping for the best...

I have allowed the newest version of FF to install, and i uninstalled the printer "Print to pdf", then downloaded the updated drivers from MS and reinstalled it.

I am having nearly the same problem as before when i select the printer "Print to PDF" and click the "Print" button, with the only variation being there are about 12 seconds that i have to choose a directory and a name for the file, then click "Print" (It seems this happened quicker than the approx. 12 seconds before). If i do not complete all of that within the approximate time frame, the "Save Print Output As" dialog box automatically closes. I repeat that this automatic closing of the "Save Print Output As" dialog box did not occur in FF v78.

I have the exact same issue if i route the output to the printer "Adobe PDF" with the "Save PDF File As" dialog box; if i have not selected a directory, a file name, and clicked "Save", the dialog box automatically closes.

Once again, i want to thank you for your interest in my problem, i do appreciate you folks being willing to go out of your way to help me in what seems like a very localized issue.

Interesting... Are you running any virus software? If so, can turn it off, reopen Firefox and try again. The next step would be to try the same steps with the computer in safe mode. When in safe mode you can just print something from Firefox new tab page or trouble shooting page.

How do I start Windows 10 in Safe Mode?

   Click the Windows-button → Power.
   Hold down the shift key and click Restart.
   Click the option Troubleshoot and then Advanced options.
   Go to “Advanced options” and click Start-up Settings.
   Under “Start-up Settings” click Restart.
   Various boot options are displayed. ...
   Windows 10 starts in Safe Mode.

Thank-you!

I am sorry to report that disabling Defender and Malwarebytes did not help, and that while successful in following your directions to start Windows in Safe Mode with Networking, when in this mode there are not any printers installed and available. so i was not able to try to print in this mode.

Yes, I just tried it myself and had the same result. ;-))

How about trying a different windows account, turning off all virus software, and then opening Firefox (do not log into the Firefox account) and see if you have the same issue.

Thank-you!

I'm confused. My impulse was to argue "Hey, FF78 worked fine, 79 did not, so why am i changing things such as my Windows 10 account login and such, it is a FF fault!", but my brain said "Listen to this person and see what happens."

I don't get it. I created a local admin account, signed onto this computer with that, installed FF to that account, didn't connect FF to my FF account, turned Malwarebytes off (but forgot to disable Defender) and have no problem printing to pdf whatsoever.

So... What is going on?

YEA!!!  ;-)) Lets see.... Now in the same (new) account, turn on your virus software and then log into your Firefox account, but now close the browser and reopen it and let see what happens.

I regretfully must report that i was wrong and made a big mistake.

My problem is caused by a specific website from which i print to pdf. From other websites i am able, but the specific one fails as previously described and as it deals with consumer credit, so i can't exactly just give the page and login credentials out.

I apologize for abusing your time; i guess i can only report the problem to the folks whose website it is and deal with it in that manner.

I'd rather have to type all the information i need to in the 12 or 13 seconds i have available than to use Edge, which does not have this issue. I was reminded of MicroSoft's tactics once again when i was setting up the alternate Windows logins and brought Edge up to download Mozilla Firefox, whereupon i kept seeing their obnoxious "Microsoft recommends you keep using this browser Continue browsing to get speed, security and privacy with the new Microsoft Edge." This kind of approach just turns my stomach and is the same that they tried ever since the first FAILED Edge.

Thank-you for trying to help me, i truly do appreciate your efforts.

Can't you open this PDF file in a new tab and then use "File -> Print or Print Preview" ?

Thank you-

Wish i could, but their webpage software forces it into one of two options, their viewing window or directly opens up the print dialog window.

I asked because it might fail because Firefox isn't sending the credentials required to retrieve this document when the print dialog is opened this way. You might be able to check this in the Web Console or in the Browser Console.

I regretfully must report that i was wrong and made a big mistake. My problem is caused by a specific website from which i print to pdf. From other websites i am able, but the specific one fails as previously described and as it deals with consumer credit, so i can't exactly just give the page and login credentials out. I apologize for abusing your time; i guess i can only report the problem to the folks whose website it is and deal with it in that manner. I'd rather have to type all the information i need to in the 12 or 13 seconds i have available than to use Edge, which does not have this issue. I was reminded of MicroSoft's tactics once again when i was setting up the alternate Windows logins and brought Edge up to download Mozilla Firefox, whereupon i kept seeing their obnoxious "Microsoft recommends you keep using this browser Continue browsing to get speed, security and privacy with the new Microsoft Edge." This kind of approach just turns my stomach and is the same that they tried ever since the first FAILED Edge. Thank-you for trying to help me, i truly do appreciate your efforts.

No problem. This is how we all learn.  ;-))