@fbalda 

Hi, please make sure that your controller is in the same network with your devices.

Heartbeat missed means that your device is losing connection to the controller. Check the physical connection. If you are using software controller, please make sure your computer is running all the time and WIFI/wired connection is stable.

If you see the device is isolated, this only happens to the device when they are in "Mesh", if so, please make sure they're in the Mesh range and have good reception. They can auto recover, but make sure the reception is good and they can reconnect to the root AP.