The network is down
Keep scanning. Every scan is kept, and parents are told when the signal is back.
Keep scanning. The phone holds its own copy of your school’s roll, so cards are still checked and students are still let in exactly as before. The screen tells you it is offline; it does not ask you to wait.
When the connection comes back, everything syncs with the times the scans actually happened. A 7:42am arrival is recorded as 7:42am, not as the time the network returned.
There is no time limit. Even if the gate phone opens with no signal at all, choose Start scanning anyway — every scan is kept on the phone and sent the moment there is signal.
Parents are not told until the phone has signal again. If you were offline for twenty minutes, those parents hear twenty minutes late, with the real arrival time — nothing is lost.
Did this not answer it? Tell us what happened — we would rather fix the guide than answer the same question twice.