No signal, could I have a dead PCIE slot?

[daiwek]

To start, here is the parts list:

• 
  Intel Core i5-7600K
  Noctua NH-D15
  ASRock Z270M-ITX/ac Mini ITX
  Kingston FURY 4GB (1 x 4GB) DDR4-2400
  Kingston FURY 8GB (1 x 8GB) DDR4-2133
  Samsung 850 EVO-Series 250GB Solid State Drive
  MSI GeForce GTX 760 2GB TWIN FROZR
  NZXT H200i
  SeaSonic M12II 520W

The story:
My PC was fully operational before any problems happened. I was sitting in discord before I decided to replace the thermal paste (Arctic Silver 5) on my graphics card. After a 5 minute job, I slotted my card into my PC and my monitors came back with no signal. Now I am running on onboard graphics with the card in the slot + it's necessary 6-pin power plugs in. It's fan is still running.

More details:

Computer is fully operational while using onboard graphics
BIOS system browser shows PCIE slot as empty.
MSI Afterburner detects only Intel 630 graphics.
Device manager only detects Intel 630 graphics.
Both a second hand HD 6850's and the GTX 760's fans spin
I am on the most recent BIOS version (which is 2.60)

My attempts so far:

• 
  BIOS doesn't have any option for selecting default video outputs.
  Tested with an working AMD HD 6850 -> also no signal
  Tested GTX 760 in friend's PC -> it outputs to their monitor fine
  Restored UEFI defaults -> also no signal

Please reply with any helpful insights or tips on how to resolve this weird bug. My guess is that the motherboard is the root of the issue. I've tried to cover my bases, but I hope somebody can help me out! Thank you.

Sarcastically mentioned that I want my motherboard to fix itself by the time I wake up to my Teamspeak buddies as I shut down my PC. I decided to give it one last try and restarted it by trying to screw down the card's expansion slot very tightly and plugging both my monitors into the card. Amazingly, my monitors turned on...

Leaving this post up for reference.

 

[rocktalkrock]

Have you checked for any dirt in the PCIe slot? Try cleaning it out.