Well, hope I can find a solution for this, I just purchased a second hand GTX 780 ti Reference Edition (Was tested before the interchange). I've tried everything to resolve the issue I've been experiencing with the card (Title of the article) since the first day of purchase. Despite the fact that, I mounted it properly to the PCI ports (used the other one for troubleshooting purposes) and also properly connected it to the PSU (650 Watts BTW), is not working nor is being detected. From my end and as per other sources, I'm thinking that is not specifically the card that may have the issue, but my PSU. Why? Well, I've tried to turn my PC without even plug the PCI cables from PSU to the card and turned out that the card fan turned on at 100% (the sound is like a mini jet or something like that) with no signal at all. My PC just booted up like normally does, no error beeps, etc.
Involving all the troubleshooting steps from various articles, I've tried them all. Even, cleaning the card gold pins with Isopropyl Alcohol thoroughly and ended up with no luck as well.
The only "extreme" methods I haven't tried yet are: Use the card on other PSU/PC, clean the card from the inside, nor use the famous "oven method" (Saw it from Linus Tech), since I wanted to see some suggestions or thoughts you might have before proceeding to it.
Furthermore, sometimes the cards turns on, the fan spins normal, then turns off in 10 or 7 seconds leaving the card lights on.
Please, let me know if I was correct in regards to the PSU not sending the needed energy to the Card or any other opinion you want to provide.
All your help will be greatly appreciated. *Sorry for the wall of text btw, wanted to be as most specific as I could. xDD
Here I left you my rig: https://pcpartpicker.com/user/antonymatos/saved/bywjcf