Assuming you're applying that clock by simply applying the XMP profile? That's step one.
Beyond that, this is pretty common with Ryzen systems unfortunately. Getting RAM to run over 2400 even can be a crapshoot. Try manually setting to 2666 and see if that holds or not. If not, you'll probably be able to set to 2400 OK but no higher. If its not holding your setting its simply that your mobo cannot clock the memory to the speed you're setting so its reverting it to default speed so it can boot. Ensure you're on the latest BIOS offered for your mobo also.
It can also depend on how many DIMMs you have. You've got a much better chance of reaching higher clocks with two DIMMs instead of four.
A lot of times you can google around about memory on your motherboard and see what other people's experiences are with your, and other, memory modules.