Question HyperX DDR4 3.200 mhz not booting on it's own

[ProdigyB]

I just bought a pair of ram sticks (2x8gb 3.200mhz red HyperX) and to my surprise the PC didn't even boot. But when I put them together with my old ram (2x8gb 2.100 Ada) the computer recognizes all 4. So my question is: Why is the PC not booting with just the HyperX and when I mix the HyperX with the Ada Ram (32GB) the computer recognizes everything?The thing is, if I wanted 2.100mhz it would be cheaper. And is it better to have 16GB with 3.200mhz or 32GB with 2.100 mhz? Thanks

PC Specs: Motherboard MSI M7, Intel I7 7700 and the ram sticks as mentioned.

 

[rgd1101]

try with 1 stick and change the xmp profile?