Currently (on Android) if an invalid token is entered in the phone app's settings page, the token is simply rejected and removed from the list of tokens. It would be nice if, instead, there is a message that indicates that the token is invalid (and perhaps an error code or an appropriate/helpful error message). Additionally, rather than simply removing the rejected token, it would be neat to keep it and allow the user to edit the token which is probably a simple typo correction. This would allow the user to fix the problem token without having to re-enter the entire value.