Help with a Mystery Motherboard Issue – It’s Not Posting!

I sold my old motherboard, a B450 Aorus M, to someone who recycles and flips systems. This board was working perfectly until I switched to my current AM5 build back in January, and it's just been sitting unused since then. The motherboard traveled in its original case for years without issue, so I don't think it got damaged during transit.

After the buyer put everything together, he reached out saying he couldn't get the system to post, despite both of us being pretty knowledgeable about building and troubleshooting. The board was getting power, all PSU cables were connected properly, RAM was seated in the slots, and the RGB lighting was working. However, the system didn't respond at all when he pressed the power button or even when he jumped the prongs. We even replaced the CMOS battery just in case.

I spent hours troubleshooting with him online before visiting in person. Our main theory is that the power header's traces might be damaged somehow. I was extremely careful when transferring my components to my new setup, and to my knowledge, no liquids ever touched the board, which had been functioning fine for at least four years.

How can this happen? Is there anything we might have overlooked or anything else we could try? I can share more details or photos if needed. The BIOS version was F62, and the buyer used a 5600X CPU, which I thought should work fine since it was previously running a 5800X. Any help would be appreciated!