Hi, I have the ASrock Fatal1ty Z270 Gaming-ITX/ac Motherboard paird with an i5-7600k and a 16GB kit of G.Skill RAM.
The system isn't overclocked at all, running base clocks. Each RAM is recogniced by default with 2133MHz and 1,2v
I tried putting both Dimms in at the same time, which results in black screens. But if I pull out 1 Dimm it works fine, doesn't matter which one. Both Dimms work in each Slot fine, so i belive the RAM is fine. Do you belive it's some sort of BIOS incompatibility or it's more likely that the memory controller is shot?
I firstly would boot with a single dimm, and then update the bios. Then see if both dimms work then. The memory modules allways get recognize at default 2133mhz or 2400mhz. To get them higher you have to set them manually, or enable xmp profile.
It could be an issue with the memory kit, modules not working well together. However that would be pretty odd. But eitherway if a bios update doesnt solve anything. Then i would firstly return the memory kit.