Gpu issues or not

[Drhandula]

Okay so first of all do excuse me for my weak grammar as english is not my native language. Now i've been building a second pc for at my girlfriends place and was installing steam on it yesterday. Today i wanted to turn it on and everything lit up however my monitor shows me no signal. I decided to check gpu by switching from the main build one and that one worked i got into bios(i had it assembled on the table no storage connected) 

 

Now you might think clear and easy gpu issue. Well i decided to put the girlfriend pc gpu in my main pc to be absolutely sure and it worked there. So now i'm completely lost as to what to do. On a side note both are the 1080ti but different brands. 

 

Tl;dr 

New gpu works in 1 pc but not the other my other gpu works in both can't switch them due to size

[Guest]

I would start by updating the BIOS's on both motherboards and both gpu's.

 

If that doesn't work, some more info on the system components would be good.