Sign-in says my account uses a connected provider. What does that mean?

It means that account was created with Google or Apple and has never had a Creta password, so there is no password for the form to check. Close the email and password fields and use the Continue with Google or Continue with Apple button instead — whichever you originally signed up with.

Resetting the password will not help here: the reset email goes to the same address, and the provider button is the shorter route to the same account.