We had a power outage a couple days ago and I've got about 11 APs (all R710s) that have a blinking CTL light and are showing as Disconnect on the vSZ-E. I've tried rebooting them, checked VLAN settings, etc. I can successfully ping them.
Looks like it's having trouble finding the controller but I don't know where else to start troubleshooting.
Got a "Me Too" notification so I thought I would update. Ended up going to each AP, used a paper clip to hardware reset them, and joined them back to the controller one by one. Took a while, but now all are accounted for and the controller sees them. It's happened a couple times more as well, super weird. When it happens they keep their configuration and work, the controller just doesn't see them.