What operating system?
Have you installed the latest driver for the card that supports the operating system?
If the installation of the correct driver doesn't automatically give you pictures, you may need to plug your video lead into the mother board display output to get pictures while you figure this out.
Then go to Device Manager, select the new graphics card in Device Manager/Display adapters then Enable or set as default device (depending on OS). Then change the video cable back to the new card & see if it worked.
You can also from there; right click on the Display Adapter Device & select properties, select the events tab & check if it has been installed correctly.
The General tab will tell if the device is working correctly.
You can also from the Driver Tab select Update Driver, though I have found that Windows doesn't always install or acknowledge that there may be a more appropriate driver, so I go to the Graphics Card manufactures website & install the correct driver using their instructions & that solves the issue.
A pic to show what it looks like when installed correctly.
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