To fix the "registration failed" error in Samsung Messages chat settings, you typically need to deregister your number from Google’s RCS servers and wait for a cool-down period
Once deregistered, do not attempt to register on your phone immediately. Wait at least 8 to 24 hours for the servers to completely clear your number's profile. samsung.com 📲 Method 2: The Google-to-Samsung Handshake samsung messages chat registration failed fixed