Google services fails intermittenly with FireFox

Solution 1:

There are many reports of this error. Below are some workarounds, at least until Firefox developers fix this bug. Restart Firefox after applying each one. These are not a persistent and the bug can return.

1. Firefox Bug 1510386 defines the cause as switching between Firefox Nightly/Beta and Release Firefox. The solution is to unregister the service worker for Gmail:

   • Go to about:serviceworkers
   • Find the entry for Gmail
   • Click unregister
   • Refresh Gmail.

2. Another solution is to reload the page without cache by Shift+Reload or Control+F5.

3. Clear cache and cookies in menu Settings > Privacy & Security, under "Cookies and Site Data" click "Clear Data…" while selecting all options.

4. Delete the storage folder for Gmail. Mine is found in folder
   C:\Users\USERNAME\AppData\Roaming\Mozilla\Firefox\Profiles\2lrpqlkx.default-1624267825608\storage\default\https+++mail.google.com
   (the identifiers may be different for you).