If a student takes the exam in a regular browser - and you have activated cheat protection - the student's exam will get locked if it loses focus. The student will then have to provide an explanation and you will get notified in the monitoring view. Depending on the cheat protection settings, you also have the possibility to see for how long the student has been locked out.
Why does an exam lose focus?
The exam loses focus if a student tries to switch tabs or programs or read something else on the computer, but also if the student's screen saver goes on or if the computer wants to update itself.
It can be a good idea to ask students to turn off the screen saver before the exam, but the best way to prevent this from happening is to use the high-security mode. Then the screen saver and notifications are automatically turned off and the student no longer has the ability to access other programs or tools on their devices.