In a scenario where a customer has multiple Wireless LAN Controllers (WLCs) running N+1 redundancy with Access Points (APs) equally distributed, the critical APs must have priority in case of a WLC failure. If critical APs remain unregistered during a WLC failure, it indicates that the AP failover priority is not enabled globally on the backup WLC. Enabling AP failover priority ensures that critical APs are given precedence over other APs, allowing them to register with the backup WLC first.