The client will not show up in the user table unless it successfully obtains an ip address. One think you can try is to upgrade the driver on the laptop to the latest version.
If that doesn't work, you can enable debugging for that client:
(ArubaMM-VA) *[mynode] #cd /md
(ArubaMM-VA) *[md] #configure t
(ArubaMM-VA) *[md] (config) #logging user-debug <mac address>
(ArubaMM-VA) *[md] (config) #write mem
Wait about 60 seconds for the debug command to propagage (you can type "show switches" over and over again to monitor this
Try to associate the device to the SSID and allow it to fail. Your challenge will be is that we do not know what controller the device will end up on, so just SSH into one of the MDs and type:
"show log user-debug all" and see if there is any traffic from that mac address. If there is none, SSH into the next MD, type "show log user-debug all".
If you don't see any messages, keep going until you find an md with debug messages for your client.