please take a look in to the logs of the Controller .
What do you get here?Which message.
>>>>>On the controller logs we can't see nothing about this fail.
If not please set the AP and AC log level to informational and configure a Syslog Server in order get more info's in the Controller logs. (Controller-> Logs)
>>>>>Wireless Controller Log Level: Information
>>>>>Wireless AP Log Level: Information
Please set one of the Ap to factory default over the AP CLI ( cset f ) and delete the AP from the WebGUI as well.( AP Bulk conf)
>>>>> This is another problem, a lot of times, some APs is down on controller but reply to ping and you can do a "cset factory" and the IP come to controller up again, but you can't see logs of fails.
Let's see if this maybe helps.
Check if you enabled secure connection - Controller->Network->Secure Connection.
>>>>> Yes we have Secure conection between controllers.
Other option would be if you have 2 DHCP Server with overlapping IP scope for both COntroller?!
>>>>> Only have one DHCP server per campus. Not overlapping
I assume HA is up.
>>>>> HA is up.
If nothing helps please open a case and GTAC should work on this.
>>>>> Thanks, we'll open a case on GTAC.