Hello Dimas,
To start with, make sure that:
1 - The firmware on the controller supports the AP7522: >show version
Check to see if you have an AP7522 profile: >show running-config include-factory | grep profile
2 - The AP7522 and controller can see each other. >show mint neighbors
3 - You have enough licenses for adoption of additional APs: >show licenses
4 - The AP7522 is not behind a routed switch. In this case you will have to configure additional parameters for layer 3 adoption
Thank you,
Chris
Christoph S.