Same thing happened to me. I had a Ryzen 1600 and a x470 from my wife's old computer that had been shelved for about a year, she needed to update to Win11 for work and it was better deal to buy a bundle at Microcenter than to just by a new processor, those were the days......, so I decided to use the existing parts I had to build a family PC. So I checked that a 5500 is compatible with my x470 but when I put it in I would get a RAM fail error. I thought the RAM and MB had gotten damaged at some point. I put the old processor back in and everything worked so maybe the CPU was bad out of the box. I was literally working on the return process when I decided to check Gygabyte's website to see if there were any notes for the motherboard. There it was, an update to add compatibility to the MB but I was on r6.0 and needed to get to r62.0 and figured out the hard way that I couldn't just install the latest version, there were specific versions that had to be installed first.