I had this exact issue with an AP-65 last week. The AP was showing up on the controller and in Airwave but was showing zero clients connected to it (see screenshot). When I sent the apboot ap-name command from the controller the AP would stay up and not reboot. I manually rebooted the ap by killing the switchport and the AP came back up and started working as it should. That only lasted a day or two so I replaced the AP with a known good AP and it had been working fine ever since.
I only discovered this issue because a student in a dorm room complained that his signal strength suddenly got worse. I am wondering if this is happening with other APs across Campus. Does anyone know of a way to check this other than looking for APs with zero clients?
I am running 6.3.1.16 on 72xx controllers with a mix of AP-65, 70, 85, 93H, 105, 115, and 225.