When using the example Arduino MQTT code from here…
I’ve noticed that it takes around 10 minutes from a device going offline to the device status changing to Offline in the App/Web console.
In this example, I powered-up the device and waited around 5 seconds after the web console status changed to “Online” then unplugged it.
The device continued to show as online for the next 10 minutes, when it eventually changed to offline…
If you try to ping or reboot the device during the period that it’s unplugged, but still showing as online, then the server reports that the device is offline 
Pete.
