You're not giving anybody enough info to work off of, so here's some basic troubleshooting. Have you made sure the card is installed properly? Did you try a different monitor? Maybe the HDMI cable is to blame, try a different cable. Try a different display method, it might be that the HDMI port on the card is non-functioning and would need to be repaired or returned. Does your motherboard have the primary display device set to integrated graphics?