Hi there,
Was this new gaming PC shipped to you or did it have a bumpy ride home? If so there is a chance the graphics card might have come a bit loose from the motherboard and would require being reseated. Another possibility is that the power cables running to your graphics card might have become dislodged.
First thing I would do is make sure you unplug your PC from the wall, open up the side, then take a look and see if anything looks loose. If you don't have an ESD wristband make sure you constantly touch the metal on your case as much as possible to avoid giving your components electrostatic discharge.