>>285176448
If you don't get a POST screen, back to basics. Remove everything non-essential, that is, motherboard, CPU, 1 stick of ram in the first slot. No GPU, no drives, see if it POSTs.
If you still don't, try a different RAM stick. If one of the sticks works, there's your first problem.
If you can't POST even with nothing but CPU and RAM, you might need to re-seat the CPU or you might've damaged the pins, or the motherboard might be faulty.
>>285178208
As this person said, make sure the power ATX12V and EPS12V are connected to the motherboard.