If the alert below is shown in your app, this means that the login code invalid. Check if your are using the right login code.

Please note that the login code for your app can differ from the code that you use to unlock your phone. 

You can attempt your login code 3 times on Android, 5 times on iOS. After that, you are automatically logged out, and you are required to provide your email address and password. After logging in with your email address and password, you can choose a new pincode.