This might happen for several reasons. Check the last position and transmission time of your device, maybe it's still in the departure airport.
Maybe your luggage is still flying in a wrong plane. Don't worry, you'll be notified as soon as it lands. There are also other possibilities, such us the device is out of battery (we recommend to charge the device before each flight) or maybe the cellular network in your destination is not compatible with Wimbag SIM provider