Metal Graphic card out of order at old mac with Mojave

[supersaian]

Hi,
I intalled mojave on my old macpro with a new metal graphic card, but the card turns to no display, the monitor also say it does not receive any signal. Can i change back using my old display card? Will the mac os boot up if i do so?

Please help.

 

[northernmunky]

What GPU is installed?