Question Replaced fried motherboard, now computer won’t start! PLEASE HELP!!

Aug 14, 2020
So I fried my motherboard (I left it in my trunk for an hour and my beep code told me it was PSU or mobo) but my pc was getting power and would start like normal it with no display, but i would get a long beep (IBM) and looked up the issue. I figured since it was turning on like normal, it had to be the mobo. Once I finished putting my pc back together with a new mother board, it is not powering at all. Actually,. The fans and LEDs spin for a split second and than it’s back off. All the LED fans seem kind of dim. I would also like to mention, the CPU fan will not spin at all. I plugged it into a 4 prong system fan slot and it span for a half a second one time, and than didn’t another time. Before I started the build, the cpu fan and everything span and LEDs were fine. I’m really stumped and so is my extremely tech savvy friend. We tried everything. Please help idk what else to do :(