Sorry to jump on this thread, but I just thought id share an experience I had with my RyZen system when I first got it last year, sounds very similar to yours, and I was convinced it was the CPU, I wasn't getting any display either, Gigabyte AB350m mobo too, just suddenly happened one morning, I spent 2-3 hours trying to trouble shoot the problem, it would switch on but just wouldn't post, was working fine the day before, even trying to clear the cmos didn't seem to do anything, eventually, I removed the CPU powered on without it installed, switched off and reseated it, tried a few different items to clear the cmos as I don't have a jumper cap, kitchen knife to short the pins wasn't working, my car key did, go figure, fired straight up, im sure mine was stuck on the CPU and RAM led though, both together, I hated that board to be honest, but AM4 boards were very hard to get hold of in the beginning and I just got what I could at the time, very soon got rid of it and brought an MSI mortar, one of the best boards I ever had.