Random Mac Lockout (Can't sign in)

Not sure if anyone has experienced this before, but I've not got any response from the Chatbot Support so I'll take any help I can get.

I'm the family organizer on a MacBook Pro (M4).
I set up a Guest account with its own email so I can put it on my spare MacBook Air (M2) so that it can access one vault, as it is a shared laptop.

1Password was working fine on both machines, following a recent security scare, I decided to rotate all passwords. And then the MacBook Air stopped logging in.  The error message is just:
"Can't sign in. The email address and the Secret Key are not correct".

I know they are correct because I have used them to log into the MacBook Pro.

Things I have tried:
- Recovered password
- Deleted Apps, Extensions
- Created an entirely new user account and tried again.
- Login in just via the browser
- New App install
- Deleted Apps, Extensions, Libraries, Preferences, Flushed caches etc. Restart.
- New App install (this still showed up the option to sign into the old accounts which I thought is weird)
- Deleted Apps, Extensions, Libraries, Preferences, Flushed caches etc. Restart. Attempted web login via Chrome incognito.

Despite trying to remove everything, it still feels like the MacBook Air is mixing up the old and new accounts. when I am logging in.