If your application for an ETIAS travel authorisation is refused, or if your ETIAS travel authorisation is revoked or annulled, you will receive an email indicating the grounds for the refusal and the authority that took the decision.
You have the right to appeal. The email will include information as to which European countries you should appeal to and describe the relevant procedure. Appeals are handled in accordance with the national law of those countries.
If your travel authorisation is revoked at your own request, it is not possible to appeal against the decision.