Just curious, what version of the Oculus software are you running? If you go into settings and then general, scroll to the bottom of the screen, it should be oculus app 1.16.
Will you try a couple more things before giving up?
Remove the oculus software and reinstall it. Then do the following.
First download oculus tray tool from here
https://www.dropbox.com/s/k3srn92fzf3utbs/OculusTrayTool_0.69.2.zip?dl=0
Unzip it and run the app using admin rights. When the app starts, click the boxes that say start with windows, start minimized and use Audio Switcher. Then in power options check to make sure your current power plan is high performance. Also in the USB selective suspend, set that to disabled. Ignore everything else for the moment. You can close the app if you want now. If the PC isn't set to high performance, set it to that now, just for troubleshooting purposes.
Now reboot the pc and go into your bios. I don't know what memory speed you have but try to disable XMP and set your ram speed to a lower speed, try 2666mhz.
When your pc boots backup try the rift and see what happens.
Thanks so much for all your help Melmac - I've tried all of the above, but still nothing
I'm going to pop out now, and I will pop by a physical computer competitor store and see if they are selling any USB 3 PCIe cards - If not, I'll waiting until next week