Hi,
I just checked it on XP11.00pb11, with TrackIR 5.
You need to start the Track IR software, make sure everything is working well on the integrated display. You can set the key commands to pause/start, center the view and even adjust the precision.
Then, with the software still running, you need to launch X-plane. just enabling it as you mentioned made it work. make sure you are in the 3D cockpit view.
My computer runs with Windows 8.1, and my track IR is the first one (quite old).