Okay surprise surprise.. with two cards if I toggle HBC on card #1 it works just fine. If I toggle HBC on #2 (previously working) now card #2 disappears from Crimson.. it's always the "last" listed card in Crimson. This is quite interesting.
Dude, have you flashed your bios to the latest version?
Otherwise try another mobo.
Or play around with the PCI-E settings in bios. It sounds like there could be some inconsistencies there.
Yep flashed to the latest version. I've tried PCIe Gens 1, 2, and 3.
I'll be grabbing a Z370 mobo from Microcenter this afternoon.
Let us know how that works out. Which mobo did you use so far out of interest?