I had similar issue using Avaya 4850 switches.
issue ended up being the LLDP command limiting power to individual ports.
this is the command from Avaya CLI that limited ports to 802.3af
no lldp tx-tlv port 1/ALL,2/ALL dot3 mdi-power-support
Once command was disabled, AP's started functioning at full power. Power LED changed to green. AP did not need to be rebooted.