If this is affecting all engineers, check that the server hosting the mobile app is running and that IIS is running. If this is affecting only a single user, check that they can access the internet from outside the app. If they can, work through the steps below:
Log in to Access Administrator in order to update AMS users.
Click Users.
Double-click the user unable to log in.
Edit the user's username. Try a shorter one — a username of 35 characters or more can cause this issue. For example, try [email protected].
Click Save and Close.
Try logging in as the user. If it still fails immediately, contact support. If the login loads, the user should be able to sign in successfully.