I am happy to report this is now working flawlessly for me! The quick answer: I plugged my PCIe card into an emplty 8x slot. I know HTC recommends a 1x or, at the most, a 4x. So I never thought to try my 8x. The only reason I did, was because I only have two 1x slots and one is hidden under my GTX1060. So, out of desperation, my empty 8x was all that was left.
I will add one more thing, because I shouldn't rule it out. When I moved the card and booted up and loaded Steam, there was a SteamVR update that loaded as well. I'm not sure what that entailed, but I guess there is a 50% chance that did it as well. To test it, I would have to move my card back to the 1x slot, but now that it's working, I'm not going to jinx it.
So, if you haven't already, try moving your card to an 8x PCIe slot.
Good luck,
Scott