I was given three AIR-LAP1242AG-A-K9 Cisco wireless access points that had previously been used at another site. I was told to connect them to a Cisco 4402 Wireless LAN Controller. I reset all three APs back to their default configurations and plugged them into the network. Two of the APs appeared in the controller's Wireless APs list. One of the APs did not appear in the list. I verified the non-connected AP received a valid IP address through DHCP and I was able to ping the AP through the controller's web interface. I unplugged a connected AP and replaced it with the non-connected AP (using the same cable and port). It did not fix the problem.