Hello Gary,
The AP 621, 622, and 650 are EOL and were added in v5.9.0/v5.9.1 for transitional purposes only to assist customers to migrate to newer AP platforms. Moving forward, newer firmware will not be available for these AP models and customers should be refreshing their APs if they wish to upgrade to the latest.
Though v5.9.0 and v5.9.1 have the firmware for the above AP models on the wireless controllers, including RFS4000/RFS6000, engineering does not support these APs on the newer code.