When the sensors are activated but don't have any LoRaWAN connectivity (the network protocol we use), the sensors will show an exclamation mark on the map (see picture below). This is to indicate that we have to bring the sensors within reach of a gateway (transmission device) within 5-6 months in order to make sure that we do not loose the data. 

If you want to know more about the LoRaWAN protocol we use, feel free to read our LoRaWAN guide: LoRaWAN: The Basics.