That's likely due to the exploit on your instance.
Most instances as a precautionary measure invalidated all login sessions.
You need to clear cache in tbe app and/or just delete your login and readd it.
I had to do it for Jerboa as my instance admins took the precautionary measure that yours did as well (though it was more necessary for lemmy.world aince they were jit hardest with the exploit)
Had this issue with Liftoff last night, but clearing the cache on the app and relogging fixed my issue. Liftoff had another update today, so hopefully that was a fix for this bug.