I experience similar things with WMR recently, and it worked quite well before:
Launching DCS in VR only seems to work once, immediately after rebooting my PC. Any subsequent launching of DCS for VR ends up with the WMR window minimized to the top-left corner of the screen, the displays of my O+ staying black, but Steam VR is running without error message, and DCS launched in VR mode on my desktop.
Seems like maybe one of the recent Steam VR/WMR updates caused this, but I am not sure...