Devices go offline because of connectivity issues.
In the event your device experiences connectivity issues, your device will display either an 'offline' label in the bottom left part of the screen (if the playlist has fully cached on the local device) or it will display a spinning wheel along with the words 'connecting' (if the playlist has not yet cached to the local device).
The following reasons may be the cause:
Internet is down
Firewall prohibiting a connection
How to resolve the above issues.
WiFi/Network Issues - Check that your device is properly connected to your local network (either the WiFi or Ethernet connection is active and the device has an IP address).
Internet is down - Work with your internet service provider to reset your internet connection.
Firewall prohibiting a connection - Work with your IT department / System Administrator to relax security measures that may be preventing TelemetryTV from running via your network.