Kevin's RAM was failing so he put it into another channel and it worked. Leo says the motherboard manual will show him how to install RAM and sometimes he'll need to put the RAM in pairs. A slot may be bad.
Should he build a whole new machine? Would it be faster? Leo says that it may not. But if he fixes the motherboard, it might. SSDs are probably fine to keep. The chatroom says that the memory should still work, just not in dual channel.