I have the same problem, same system, 5960X with an Asus X99-A
I went through a hell to make my Vive Pro working, but it´s finally working (also the hardware was not the problem because I tested it in a different PC)
But the cameras are not working at all, no matter in what USB I connect it, 3 or 2, no matter, cameras are not working, I enabled everything in privacy for the cameras, and tried the things said here, I even reinstalled Steam completely, nothing seems to be working.
I also have Windows 10 Pro 64Bit 1803
Please, help.