- Make sure that the current software version installed on the WLC is compatible with the AP-type (google on cisco wireless compatibility matrix).
Make sure you have route reach ability from AP to WLC. Try to ping the WLC from the same subnet on the switch where AP is connected.
If you have network reachability and still cannot join WLC, please post show ap join stats to look into it.
Unable to ping what? Does the device get a gateway ip address?
If does and still does not ping on the network, you did some wrong configuration.
-If I helped you somehow, please, rate it as useful.-
Please check the access point connected switch port have the right vlan configuration to reach the wlc.
Once after connecting the access point on the switch, please take the console of the Ap and check whether the access point getting IP address or not.
check the wlc reach ability from the AP end.
Managed to find out the issue the 2800 series are pre-loaded with MObility Express images so it needs to be converter CAPWAP in order to join them with a WLC
just wanted to share so it might help someone