Device offline is defined as the time when dozee is not connected with the internet and hence not uploading data. It can be because of the following reasons
1) Dozee is powered off
2) Dozee is not connected to the internet
No internet connection
Modem is not connected
Modem is very far away from dozee
Overload of devices on modem
Set this alert if you are not expecting Dozee to go offline in a specified time period for a specified duration.