In the first section of the "Sign-In Setup Options" window, you can specify how long a volunteer can remain idle, while signing in, before the system times them out. If the volunteer does not finish signing-in during this time, they will be returned to the login screen.
Here you have three values: "Sign-in timeout," "Sign-out timeout," and "See supervisor timeout."
The default sign-in and sign-out time is 20 seconds. If the system times out while the volunteer is signing-in or signing-out, they will need to log-in again OR you can modify the time(s).