Start by upgrading your controller to 8.5.0.10 or 8.6.0.5
Than start with cpsec auto-cert
On your ap go to convert and convert it to campus ap.
Be sure to add ( just in case ) your ap mac to campus ap whitelist in your controller.
Check pings from controller cli to ap IP
Check show log security 50
Check show log errorlog 50
Check show log system 50
Share it with us. The more info the more help we will be able to provide.
show ap database-summery will be helpful also.