Just to get my 'four penneth' in
Make sure that the car has not gone to sleep and the car and your phone have good wireless signals.
Enter the phone number, choosing the country code and entering the number with no zero, OR enter the e-mail address, that you originally used to set up the account.
Enter the password, noting siteguru's advice.
Agree to the User agreement and Privacy Policy just below the ‘Login’ button. You may need to ‘Zoom out’, or scroll down, or change other phone settings, to ensure you see the whole screen.
Tap the Login button. If this is ‘greyed out’, all the required information has not been entered correctly.
If it isn't greyed out, you should get access to your account. DO NOT 'unbind' the account from the car, this should not be necessary and may only cause problems. Don't expect all the car's information to be shown correctly. Get used to the app before doing anything drastic. You can however delete the cache from the settings menu.