trickerzyt :
Would that explain the GPU stop and starting??
Of course.
As I understand, it's a new build, and it never booted in this configuration, i'm 99% sure the bios is not updated for the 2nd gen of ryzen. So it will not start (it will spin up a bit, maybe even some flashes from the gpu, and then halts at CPU)
You need a 1st gen am4 cpu (ryzen 1xxx or other from same gen) to update the bios to support the 2nd gen of ryzen.
If the motherboard is new you can contact the vendor to help you with the update of the bios. Send it to them.
Or do it yourself if you can get a hold of 1st gen cpu from a friend or something.
300 series of chipset is for 1st gen, 400 series chipset is for 2nd gen right from the box.
300 series chipset has updates to support the 2nd gen but most likely the mb sits in that box befor the update was available so you need to the update the bios by any means.