@Setlec 

Explanation of Isolated: (For APs in the mesh network only) The AP once managed by the controller via a wireless connection now cannot reach the gateway.

You can rebuild the mesh network by connecting it to an AP in the Connected status, then the isolated AP will turn into a connected one.

For detailed configuration, refer to this link: How to Build a Mesh Network via Omada EAP in Controller Mode

If the Mesh EAP turning to Isolated frequently, maybe the installed location is too far away, or too many obstacles, making the wireless link unstable. It's recommended to find a better location to install the mesh EAP.