If you are receiving the below error then please try the below steps.
- Install version 8.1.5 (ensure you have the latest version of the Arsenal app)
- Go to menu (three lines top right of the page on Arsenal app)
- Open settings
- Under "Advanced" there is a "Clear keychain" button, click on that. That should force the user to be logged out completely.
- After the above steps, attempt to log in again.