Hi @user_3445655,
If an AP is in fault state, it indicates that the AP fails to register with the AC. Run the display version command on the AP to check the AP version. Run the display version command on the AC to check the AC version. If the AP version and AC version are compatible, then kindly follow the steps below:
Check whether the network connection is normal.
Configure the AP and AC to ping each other.
Check whether packet loss occurs and whether the MTU value is small on the intermediate network.
If NAT traversal is configured on the intermediate network, check whether NAT communication is normal.
Run the display cpu-defend statisitics wired command to view the value of Drop Packets of capwap packets in the statistics on packets sent to the CPU. If a large number of packets are lost, check whether the threshold is set properly.
Thanks!