The PC will post without a drive attached. Disconnect all drives until you figure it out
9/10 time when a new system wont post its because the CPU power is not connected or GPU power
Only attach one stick ram, CPU power and GPU. Short the PWM front header and it should post
If it still wont post. Check the BIOS reset jumper and see if its in the correct position (manual)
Do I see an adapter on the GPU power? Get a proper PSU