Is the AP still accessible via its IP address - ie. can you ping the device and/or use SSH (on TCP port 2335) to connect to it?
If so, you may want to try to ping the AP from the BSC's diagnostics screen. Also, you can try to factory default the AP if you can log into it.
If you cannot communicate with the device, then the BSC likely cannot either. You will want to check the switch where you have connected the AP. Try a different switchport to ensure the issue is not with the switch.
If you can communicate with the AP, but the BSC cannot, then you want to check your firewalls and/or routers. Granted in a BSC system, the BSC itself is likely the router so you may simply need to check your layer settings in the switches on the managed side of the BSC.
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