Monitors not working

[Subwoonfer]

I may be a noob at this, because I probably really messed up... I have been building a new PC. Everything came BUT the GPU. I wanted to at least POST the system, so I went to my dads computer, (with his permission of course) unplugged it, and took out one of his two 1070TIs. They were connected by an SLI bridge, and I simply took it out and I had both monitors plugged into the TOP GPU. This was the primary GPU. I went to my pc and put it in there, posted the system and removed it. Yes MY PC works... I put his GPU back, and turned on the PC (yes i put the SLI bridge back). The PC booted perfectly with the RGB keyboard lighting up and all the fans and the ZOTAC logo lighting up on BOTH GPUs. The fans came on on everything (including the GPUs). Guess what didn't turn on? Yeah... the monitors. Absolutely 0 signal went from EITHER graphics card to the monitors through a DP cable. I don't know what happened exactly but here are my three theories...

 

1. I forgot to turn off the SLI setting in the NVIDIA control panel (which is nowhere to be found btw), and the primary GPU overclocked itself to death or something. (I don't know if that's a thing).

 

2. My dads cables are absolutely fricked, and I need to try HDMI or something.

 

3. The cards simultaneously burnt out with mix of bad luck and timing.

 

 

4. The graphics have traveled to the V̶̢̑̈́̋̉͋̿͛̃͐̏̅̋͊̊̀̕̕͠Ô̵͉̟̯͖̩̽͐͗̌̀͒̈͘͘͠ͅǏ̷̛̛̝̫̟̳͍̰̬͔̳̥͎̲̾̆̾̒̓̿̎͒͒͆̏́͜͝D̵̡̲̟̗̖̟̫̠͇̙̳̼͔̪̬̤͓͕̘͇̬̜̾͒͌͗͂̾̈͘͝͠ͅ

 

 

 

Also, the bottom monitor worked for a little bit, but stopped. This is how I know that the NVIDIA control panel has literally vanished. 

(I know my way around computers very well, i just don't have a clue at what happened.)

 

I cannot find the full computer specs on his computer. It was a prebuilt and i can't go to the System Info panel... because no cool screen thingies light up.

More info on the situation:

 

Yes, the monitors are on.

 

Yes, the monitors are plugged into the card and the GPU is perfectly in place and has power.

 

Yes, I have the right SLI bridge (it was working just fine before).

 

Note that I can do nothing to change any "software" problems.

 

Yes, I have unplugged and plugged the cords and cards MULTIPLE times.

 

The monitors are two 3840×2160 4K monitors. (we are using them in 1080p though, so thats not the problem lol).

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Update: I threw the primary GPU into my new PC and it works just fine! So were left with option 2,4 of MY theories. A new theory has been created... 

 

5. The whole system is doomed.

 

More info on Update:

 

I used an HDMI cable.

 

I smoothly talked to the graphics card begging it to work.

 

Second update: It randomly started working!!! I’d really like to know what happened though. If anyone has any ideas I’d love to know! I don’t even know if anyone will see this post because it’s been like 4 hours. But please, if you know what may have happened, please let me know so I don’t bust any future PCs.