@Jyn If both ram sticks work when tested in one slot, and if you swap it to the other DIMM slot and it works, then maybe try re-sitting the CPU?
EDIT: Just remembered a weird issue I had a while back. If the pc is sitting up right when you're putting the ram in try sitting it down on it's side. For some reason one slot on my old MOBA didn't like it when I had the pc sitting up right when putting the ram stick in, but when I put it on it's side and put it in, it worked fine.