If you don’t get head rotation the scanner did not find the right memory locations although it “thinks” it succeeded. Sometimes that can happen. Unfortunately there is no 100% guarantee that the scanner works reliably on every system. Hence the according message that is shown during each scanner run.
Not really a big deal if it doesn’t work for you. FOV is handled via .ini editing and unless you changed the mouse sensitivity in the game options, mouse based tracking works correctly out of the box. DirectVR tracking would provide slightly less latency, but the default mouse based tracking isn’t too shabby in that regard either in this case.