Enable all log messages on the controlller
GUI > Controller > Logs > Logs Configuration > System Log Level > Information
Reboot the AP and you should see the following messages in the controller log for the AP registration ...
![2c39f3e7f4da4316affaa6fad9a4824f_RackMultipart20170830-13530-1nsmqyv-EWC_AP_registration_inline.png 2c39f3e7f4da4316affaa6fad9a4824f_RackMultipart20170830-13530-1nsmqyv-EWC_AP_registration_inline.png](/t5/image/serverpage/image-id/5395iD8DDC4D60625EA65/image-size/large?v=v2&px=999)
If the last message (the one on the top = blacklist......) is missing the AP isn't fully connected to the controller.
-Ron