According to the AP-215 datasheet here: http://www.arubanetworks.com/assets/ds/DS_AP210Series.pdf it requires that the controller run 6.4.2.0 or above.
Also you would need to provide dhcp to access point and the access point should share a vlan with the controller so that it could discover it.
Type "show ap database" to see if the access point is up or has a flag next to it.
Also type "show log system 50" to see if you can get an idea of why the access point would not come up.