Question Why does my motheroard have a red light on cpu

The first thing I'd try is checking every cable connection, although I'm quite certain you've already tried that.

Secondly, try reseating your CPU as I've encountered a few ryzen builds with the CPUs not seated correctly posting the same problem as yours. After aligning the triangle give it a GENTLE wiggle and check every corner of the CPU to see if it's properly seated in there. While you're there, verify if other components are seated properly as well.

Also, try running with the bare minimums... 1 stick of RAM, no storage drives.