Bookmarks Are Gone

If Firefox starts up after an update without your bookmarks and other settings, check whether your data is available in a different profile:

Inside Firefox, type or paste about:profiles in the address bar and press Enter/Return to load it. The About Profiles page will open. This page should list at least one profile and could list many.

The profile that Firefox is currently using will show:
This is the profile in use and it cannot be deleted.

Please do not delete anything here; don't use any Remove buttons.

Do you have another profile named default or default-longnumber listed on this page? If so, you can check whether it is the one you were using recently by clicking its Launch profile in new browser button.

If it isn't what you want, simply close that new window.

If it IS what you want, click the Set as default profile button for that profile on the about:profiles page. Firefox will use it automatically at the next startup.

For more information see Recover user data missing after Firefox update or reinstall.

Note: If your bookmarks are not available in another Firefox profile, see Recover lost or missing Bookmarks for other solutions.

There has to be another issue because it won't even let me create new bookmarks now. When I open a new URL and try to save the tab bookmark it just won't save it. What is the issue please?

If you can't read AND write bookmarks altogether it usually means some other app has locked the files — the easiest solution usually is to shut down the browser and restart the whole computer to give the profile another attempt at loading — and hopefully everything will be accessible again on relaunch.

So I tried to restart the computer as well as Firefox and I still see the following message. Mind you, there is no other application open.