I understand that you already did go through the trouble shooting steps, but this almost certainly is some kind of hooking conflict then. Ideally disable everything running in the background.
Did vorpX show a dialog that says ‘Attaching to: wow.exe’? If so, in case of a hooking fail after a while (about 30secs) this dialog should offer an option to install a hook helper to the game folder. That should be the first thing to try.
Apart from that: if you use any other AV program than Windows Defender, please try to remove it for testing purposes. Unfortunately some more annoying AV programs can’t be disabled unless you remove them. Windows Defender will kick in instead, so there is no risk involved. Third party AV is pretty much unnecessary in Windows 10.
If you happen to use a gaming laptop or some other dual GPU setup, please also (re-)check the related section in the trouble shooting guide. Desktop viewer working, but hooking into a game not working sounds a bit like a HMD-connected-to-wrong-GPU-problem.