I am in the EXACTLY same boat as you man, I am also stumped. I have 3 GTX 1060's in my mining rig but the OS only recognizes 2 and hates the 3rd no matter which order they're in. I am also using the same ASRock motherboard and similar other hardware to you.

I am going to try that fix that q43a0ef061ej has pointed out and I will also report back ASAP.