Question PC stopped booting suddenly

[MrYasin]

Here's how it went down. I was thinking about changing my CPU cooler but because there were no correct cpu cooler height available for my case I decided to open the side panel and measure it my self. When I looked at my screen it was gone completely black so I pressed restart button and it didn't work tried turning it off with the power button didn't work as well. Only way I could turn it off was PSU switch. After that I tried turning on the PC but it doesn't even boot to BIOS, I have a mobo speaker the "beep" sound doesn't come as well. I tried plugging off rams, plugging off all USB ethernet speaker except keyboard nothing worked, plugged out everything except CPU, CPU cooler, 1 ram still not booting. Can anyone help me It's really frustrating PC was working fine for months.

Mobo: Gigabyte B450M S2H
CPU: Ryzen 5 3600 stock
GPU: Asus Turbo 1080Ti
RAM: Corsair vengeance LPX 2x8gb 3000mhz
PSU: Zalman 80+ 700W

PS: Every part is working fans gpu cpu cooler yet no boot.
Edit: I still cannot power down the pc with the power button It opens it but I have to use PSU switch to power it down.

 

[Lutfij]

I decided to open the side panel and measure it my self. When I looked at my screen it was gone completely black
Did you manage to short something while the system was powered up...like a measuring tape making contact with two metal points on the board?

How old is that Zalman PSU? What model is the PSU? 700W is the wattage and 80+ is the efficiency rating.

 

[MrYasin]

at model is the PSU? 700W is the wattage and 80+ is the efficiency rating.

It's Zalman ZM700-GV and I also started to think I might have short circuited something the metal from measurement tape might have touched the motherboard