ReCenter() on Vive does nothing

So using 2019.4 and a Vive Pro Eye I want to ReCenter the HMD during Start().
As OpenVR is only supported using the old XR manager, I've got that active with only the OpenVR device added. The HMD works fine.
However, when I issue the XR.InputSubSystem.Recenter() nothing happens. No errors, no headset reorientation, nothing. I seem to remember this always worked before and I really need it for my sit-down VR!
Anyone with any ideas either how to get it working or use another method?

Cheers!