Check the chosen login method, exact server endpoint and supplied username and password before changing playback settings. A rejection before the library loads is an authentication-stage problem. Video-decoder or subtitle controls are unlikely to fix an account form that never signs in.
Keep the values literal
Preserve case, punctuation and any port or path in the endpoint. Remove accidental formatting outside the values, but do not rewrite the password or guess a different server. Confirm that an old trial profile is not selected instead of the current account.
Ask about account status privately
An account can be expired, disabled or configured for a different supported route. The player’s generic message may not distinguish those cases. Use the established support channel with the account reference they request, not a public post containing the complete credentials.
Avoid repeated broad resets
Clearing app storage can remove favourites without resolving the underlying account status. Once the fields have been checked carefully, send the exact error and time of the attempt. That gives support a concrete authentication event to investigate. Keep the original error wording intact so an authentication rejection is not confused with a later media timeout.
