You didn't mention a graphics card, so I assume you are using the onboard Intel graphics for now. That's best when working with a new system if available.
As you power on, hold down the Delete key or F2 to boot into the BIOS.
It should be pretty intuitive to see if your memory is showing and the total amount.
Is it possible you have the sticks installed in the wrong slots?
While in the BIOS, navigate to the storage devices and see if your M.2 drive shows up.
This should give you a better idea of what's wrong.
Good luck