Hello Mohammed,
In addition to what Nathiya had suggested above, I would also recommend that the AP has the correct network time via NTP and also has access to the internet.
Also, make sure that you do not have another local controller that the AP can connect too.
The article below may help:
https://gtacknowledge.extremenetworks.com/articles/Q_A/What-are-the-prerequisites-for-deploying-my-a...
As always, if you are not able to resolve it, please contact GTAC to open a case and we can assist.
Regards,
Jason