A common pitfall with OpenXR is that inputs will only become active when the application session is in the focused state. It varies between runtimes, but any system overlays being active, or taking off the headset can drop the application out of focus. It can also take several frames before the inputs become active again after the application is focused, so debugging can show misleading transient states if you are only debugging the first frame.
If you still get the same results after several frames, and the CurrentSessionState member of FOpenXRHMD is set to focused, it could probably be an issue with the runtime. An options is to try other runtimes besides VDXR and see if they have the same issue.