Place mtrbd. on cardboard(or ESD free mat) and remove all connections and devices, cpu, etc.. Now having only the PSU + mtrbd and spkr., try to power-ON. Is there a LED on, if not, return mtrbd.. If there is, add one item back(power-OFF) until maybe the LED doesn't come on. Spkr. will beep as items are missing, etc., but when it does not beep, probable PC will work. DON"T TAKE ANYTHING FOR GRANTED. If DOA, don't hesitate to return vis proper process.
I just tried my first pc build from scratch i put everything in the case motherboard cpu everything went in fine no issues at all psu hook ups were all easily plugged in ram, hdd, and dvd drive, and graphics card all smoothly installed, now the problem came in when i hooked it up to a monitor hit the power button and nothing so i looked inside to double check all power hook ups everything looked fine, i also recently swapped a psu in my other computer without issue so i wasnt completly new to installing a psu. Upon further inspection i noticed that there was no led lights lit up on the motherboard, i remember when i swapped the psu on my other computer the lights lit up on the board right when i plugged the comp in. I pulled the motherboard out and set it down plugged a differant psu into it and also no lights. Im new to all this for the most part but my guess was the led lights on a motherboard are status lights and if there not on must be somthing wrong like a dead board any info would be awesome... the motherboard in question is a MSI 790x-g45