Reseating RAM takes less than five minutes.

It is the easiest fix you will ever try on a PC. Pop the side panel, press down the clips, pull the sticks, put them back in until they click, close everything up, and boot.

Nine out of ten “RAM not working” problems are just the stick not fully seated. It is surprisingly easy to push a stick in and have one side not quite lock. You can check this even before touching anything else: unplug, press both ends down firmly, listen for the click.

If reseating does not work, try one stick at a time, swap slots, check if the motherboard manual says which slots to fill first. But start with reseating. It costs zero dollars and often saves you from buying new RAM or RMAing something that works fine.