Hello Alessandro,
Even though the v5.8/v5.9 release notes indicate no firmware support for the AP650, AP621, and AP622, the firmware is present on the controllers, which these APs require to operate, version 5.8.5.x, v5.8.6,x, v5.9.0.x, and v5.9.1 (latest) have support for these AP models. These models are not supported by Extreme Engineering/Development. Starting in WiNG v5.9,2, these APs will not longer be present on the wireless controllers.