Hmm, first time seeing this problem. Could you check for error messages in the "Browser Console" that could be related to this failure. You can open the separate Browser Console window using either:

• "3-bar" menu button > Web Developer > Browser Console
• (menu bar) Tools > Web Developer > Browser Console
• (Windows) Ctrl+Shift+j

Click the trash can icon at the upper left to clear the window, then switch back over to your main window and try printing again.

Then switch back over to the console window. Did Firefox log any errors related to that action?

More info on the Browser Console: https://developer.mozilla.org/docs/Tools/Browser_Console

Firefox 85-86 have a preference to switch back to the classic print experience if necessary. Here's how you use it:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

(2) In the search box in the page, type or paste tab_mo and pause while the list is filtered

(3) Double-click the print.tab_modal.enabled preference to switch the value from true (new experience) to false (classic). That should look like this after the change:

You can switch back and forth any time.

Oh, "print spooler service" in windows was disabled, I may have disabled it when doing system optimization.

I only realized the above after switching to 'classic print experience' by modifying 'print.tab_modal.enabled' value to false which showed up with print service error.

Please add the similar error to 'new print experience' also.

Thank you. Let me know if I can help more

Strange Chrome allowed to print to PDF with "print spooler service" disabled.