Question about Corsair Vengeance LPX

I have bought and installed the RAM (ASUS X-99s). The following problem. The RAMs are not recognised. When coupled with the old RAM, only the old ones are recognised, when installed alone the PC does not boot at all (error 53, no RAM). What could be the reason for this? - The slots are OK - Mainboard should tolerate them - They can be installed and clicked in correctly without any problems and are easy to see. So far I have not overclocked the board. Is it possible that this is the reason? Greetings and thanks for answers!