Building PC from Old Parts Black Screen

Building a PC out of my old used parts. It booted up successfully with these same parts no problem yesterday but when removing it from the case to clean the dust it just black screens with no beeps, all the fans are on, all LEDs are on.

Mobo: Asus p8p67
Gpu: nvidia gtx 660
Cpu: don't remember off the top but it was 7 years old
Psu: 750w cooler master
Ram: 16gb ddr3 (currently only have one 4gb stick in the mobo)

I removed the ram to see if i had damaged the mobo but when I booted it up I got the 3 beeps so I turned it off and put the ram stick back in. I tried using a gtx 970 to see if the gpu was bad. All power connectors directly to the mobo are connected. Still the screen stays black no bios last time I had issues with this I took it to a local computer shop and the guy needed an electrical engineer to come in and I'm hoping I won't have to do that again
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  1. Also I tried using a different PSU that was 600w
  2. Put the 750w psu in another machine and it booted up just fine so the power supply works
  3. I fixed it lol the ram wasn't fully inserted I hate the Asus p8p67
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