Please help. Asus z170-a detect all rams 4×8 but only available 16.

Here is my system:
Windows 10 pro 64bit
Cpu : i5-7600k
Motherboard: Asus Z170-A
Gpu: asus strix gtx1070
RAM: 4×8 Corsiar Vengeance DDR4 3000 (pc4-2400) c15
Power Supply: Corsiar RM850x

It work fine except it only run at 16gm if ram.
On bios it show 4×8 gb but capacity is 16gb. I already replace the motherboard it is still the same.

Is there a newer bios version for this board?

If nothing else I would contact Asus tech support and seek their input. Theoretically it should work but you have the scenario where you are trying to grandfather in a new CPU technology generation to a chipset that was originally designed for Skylake, not Kabylake. They are supposed to work with one another but these are the kind of irregularities you encounter across generations of technology. And you would have never known there was a glitch if you had only been using 16gb of RAM. I wonder if you would have encountered this issue with 2x16 gb (if they make them that big)?

At any rate, Asus needs to know about this so they can work on the problem for others. Probably a bios issue.