Question Power but no screen input

[Syfar]

Still needs answering.

While trying to install the OS onto the SSD, a video said to unplug the HDD. I had done so, but after it wouldn't boot at all, I plugged the HDD back in, but still nothing. I had then ordered a new Motherboard, CPU, and RAM, and installed it with help to try and fix it, but that didn't work. There is power to everything (Fans/LEDS) but no screen input. I have tried taking out the SSD/HDD/GPU, triple checking everything is hooked up(always the chance I still missed something) and reseating the RAM, but still not even a BIOS. I've tested the screen on another computer and it works. I'm thinking a wire could have been damaged somehow?
I wanted to try asking here before totally giving up and taking it to a repair shop.

UPDATE: Not consistently booting, and only started twice. Im not sure why. The CPU/Motherboard keeps restarting inside.

Current upgraded system:
Operating System
Windows 10 Pro 64-bit
CPU
AMD Ryzen 7 2700X
RAM
Corsair Vengeance LPX 8GB (1 x 8GB) DDR4 DRAM 2400MHz C16 (PC4-19200)
Motherboard
GIGABYTE B450M DS3H
Graphics
ASUS GeForce GTX 1080 8GB ROG Strix
Storage
1TB Western Digital Blue
Samsung SSD 860 EVO 1TB 2.5 Inch SATA III Internal SSD (MZ-76E1T0B/AM)
Power
EVGA SuperNOVA G2 850 W 80+ Gold Certified Fully Modular ATX Power Supply

 

[rgd1101]

monitor connected to the gpu and not the motherboard output?
what connection are you using to connect to the monitor?

 

[Syfar]

monitor connected to the gpu and not the motherboard output?
what connection are you using to connect to the monitor?

Had tried both, but yes, to the GPU output.
1080p HDMI Male to VGA Female Video Cable Cord Converter Adapter for PC HDTV TV
Connected to:
AOC e950sw 19" LED LCD Monitor - 16:9 - 5 ms (E950SW) (Might be slightly different to this one, but best I could find)

 

[Syfar]

Friend says it could be that I am missing a stand off for the motherboard (Also the case doesn't have holes for two at the end of the Motherboard.)
I also re-wire management-ed everything, and still nothing.
Friend also says CPU seems to be shorting because its restarting every so often.

 

[rgd1101]

exact model of this hdmi to vga? it just a cord? you probably need a active adapter

 

[Syfar]

exact model of this hdmi to vga? it just a cord? you probably need a active adapter

It has a box on it too, and looks like other "Active DisplayPort Adapters". However, it does not have the two holes for the VGA screws in it.
This screen and adapter has worked on my old setup, as well as a laptop I tested it on.
Besides, the adapter wouldn't explain the CPU fan restarting, as my friend said means an issue.
The GPU still turns on, then after 2 secs restarts with a white light and the PC powers down instantly when I press the power button, regardless of time waited.

 

[Syfar]

Update: With friends help, we discovered a standoff behind the motherboard that was not in line with the hole. Getting tool to remove that today.

 

[Syfar]

Update-2: Moved the stand-off out from under the motherboard, and in line with the screw hole, but it's still the same.

 

[Syfar]

Update-3: Fixed now? Im not sure what did it, but I let it sit turned on with everything plugged in and after a few mins, the screen came to life.

EDIT: It doesn't turn back on consistently, and only got it twice in 30 mins.