@p @p @p @p @romin It's most probably caused by an invalid client id. In Mastadon's oauth flow, you have to pass redirect_uri param in 2 APIs, first while generating the client id and then while generating the access token for a user. bloat uses the client_website config as the redirect_uri value, if it was changed after the client registration, oauth will fail (Pleroma always says Invalid Username/Password regardless of what the actual error is).
Either that or the previously registered client id was removed from the database. Registering a new client should fix the issue in both the cases. Try `rm $dbpath/app/shitposter.club` and then restarting bloat. Recent version of bloat no longer stores the client data and regenerates it for each new session, so it's less likely to happen there.