No display from gpu

Hi, really desperate for some help.

I have a 7910 workstation dual core. 128 ram. A saas card gforce 2060. 

Everything was working until I put in à 2080 ti ultra, I took out the saas card and fitted ultra 2080 ti and put saas card back. 

Pc turned on no errors on front but it will not display. So just to make sure I took out the ultra 2080 ti and put back the 2060 which was working.

Now will not work with that either.

Can't engine what could have happened.tried with out the saas , same issue,

Took out ram, same issue, took out all the usbs ect, , same issue, changed cable same issue, eventually got advise to take cmos battery out did that same issue, reset cmos bios , same issue, it turns on, I can feel all components coming to life but just no display from graphics at all 

Any advise given would be appreciated.