Laura,
It sounds like the AP's have lost communication to the Controller, or network and are possibly still up and active, just not showing the configuration.
I would recommend investigating the ports the AP's are on, see if they are rebooting or staying active, still with a DHCP address, and if they have a route back to the Controller, or if the Controller has a route to the AP's. Can the Controller ping the AP's gateway, etc.
I would suggest opening a case with GTAC if you need assistance with that.
Thank you,
Jason