Im wondering, why my devices are listed as inactive, on the dashboard on the application server.
The devices are sending data, that can be seen under the devices.
Love the dashboard. Have you considered clicking on the graph to give a list of the inactive devices as well as the number. We currently get such a list via query to the devices table.
It will depend on how often you expect a device to check in and will be specific to your application. Some devices report frequently, some report only on rare occasions (i.e. smoke alarm), etc.