Why my plugins (add-on)have been removed?
I had a lot of plugins that after reinstalling the operating system and logging in to the Firefox account. Too many of my plugins have been removed. I need them. How do I recover?
I'm not sure which extensions "Sync" between different installations, but it sounds like not all of them Sync.
Do you have any backups from before the reinstall?
Did you use the Windows 10 feature that creates a backup for you, in a folder named:
If you have that folder, we can suggest how to dig up your Firefox data from before.