@Exejee 

Adopting status indicates that the EAP is not responding to the adopt command from the controller. For this problem, you need to check the connectivity between the controller and the EAP. This is not the controller's problem, so don't blame it alone, and you should also check the EAP110 outdoors itself. You should check that the physical connection to the front end router is correct. Usually, even if it shows up as disconnected from the controller, its wireless network may still work fine.

There is an article here that deals with this issue, you might want to take some time to read it:What to do if Omada Device Adoption Failure

  @Exejee 

It is true that our Cloud-Based Controller and EAP110 Outdoor are incompatible. Its settings won't apply to it, even if it does adopt it. Additionally, the EAP's prior settings will vanish if you adopt it to the other controller. Since switching to a new controller will erase all of its previous settings. That is the same as resetting it. Unless you reset or reinstall the controller without saving the previously recorded data, the settings you have made should normally remain intact. It's possible that you updated it without uploading the previous firmware's backup file. This, in my opinion, has nothing to do with the EAP's temporarily disconnection.