If you have remote access to the PoE switch I recommend that you shut down (or disable in the GUI) the switch port which is connected to the AP you want to reboot. Wait a minute or so and do a "no shut" in the CLI or enable it in the GUI. This will reboot the AP.
I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post to unmark it and select another in its place with the applicable buttons. If you have any additional information on this that others may benefit from, please come back to this post to provide an update. If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.