The device registers with the server in three situations:
On launch — as soon as the app starts, it sends a registration immediately, regardless of when it last registered.
Via a background check — a timer runs every five minutes while the app is open. Each time it fires, the app checks whether 60 minutes have passed since the last successful registration. If it has, it sends a new one. If not, it waits for the next check. In practice, this means the server record is refreshed roughly once per hour during an active session, not every five minutes.
When returning from the background — if the app was minimised or switched away from for more than five minutes, the same check runs as soon as the guest comes back to it. If an hour has passed since the last registration, it sends one immediately. If not, the existing schedule continues.