I've had this problem before, but I was able to resolve it that time. macOS 10.13.4, everything up to date. Yesterday, Internet Accounts forgot my LinkedIn password and would not reauthenticate. Today, it forgot my Facebook password.
- App specific password.
- Removing the account and re-adding it.
- Turning off 2-factor authentication.
- Deleting associated entries from Keychain.
- Logging out of iCloud, deleting Keychain entries, removing and re-adding the account, then logging back in.
First of all, what the hell—why does this keep happening?! Secondly, what else can I do to fix this short of reinstalling macOS?