UPDATE: I can log in using private browsing... holy shit, what is going on!
UPDATE: I can log in using private browsing... holy shit, what is going on!
https://support.mozilla.org/en-US/kb/containers
Containers do not share cookies, local storage, caches, or other persisted data.
https://support.mozilla.org/en-US/kb/profile-manager-create-...
Anyway, my last attempt will be to create a new profile. I was avoiding that because it feels like quitting. It feels like destroying everything and replanting the soil hoping for a better outcome even though you have no idea what happened before.
Has happened to me for Chrome and Firefox. Creating a new profile works. Or if you're feeling paranoid, remove any trace of it from the system and do a fresh install.
If problem persists, new profile.
If problem continues, reinstall FF.
The only plugins in the Plugins section of about:addons should be the OpenH264 plugin and the Widevine plugin (only if DRM is enabled). Both can be disabled there.
The successful login with private browsing makes me hopeful though. Maybe I'll find a solution :-)
My FF profile was corrupted once and a lot of sites stopped working mysteriously. Clearing cache didn’t help either. It has to be a new profile.