2133 to 3000

Hello. I had 4x8 vengeance 2133mhz c13 on a 6700k for a while but one ram failed after some trouble i had with my pc and i had to change the mboard(to a z270 asus) because the last one was dead(z170 gb). Now i have 3x8 (24gb) , and if i try to OC it doesn't want let me pass the 2600mhz( like i'm...