When changes such as rule updates occur in Mobile Fence, a command is sent to the device instructing it to retrieve the latest rules from the server. At this time, a Google Cloud Server (hereinafter referred to as "Cloud") acts as an intermediary between the device and the Mobile Fence server. The Cloud and the device are connected via a unique key; if this key value is revoked for any reason, a "DEVICE_UNREGISTERED" message will appear during "synchronization."

• In most cases, the DEVICE_UNREGISTERED message appears because the key between the Cloud and the device is revoked only when the app is deleted.
• Other reasons for key revocation are unclear, and recovery is only possible by reinstalling the Mobile Fence app.
• When in the DEVICE_UNREGISTERED state, real-time rule updates and device commands cannot be sent to the device; however, the Mobile Fence service (monitoring, blocking) continues to function normally, and timeline logs are still uploaded properly.