Question Suddenly dead motherboard

Jan 23, 2022
Hey guys, I've run into a bit of a problem.
I've some experience in building PC's and I'm upgrading one for my brother atm. I'm giving him my old motherboard, a gigabyte B150-HD3P. When it came out of my PC, it was in working condition. Now I have built the whole PC, it is not powering on at all. No lights, no fans, etc. I've tried removing and reconnecting every cable. I tried shorting the power on instead of the button. I tested my PSU using his old motherboard, which worked fine. I tried his old PSU, worked on his old mobo but not this one. There is simply nothing at all. Anyone know how I can troubleshoot further?