If the VGA light on your motherboard stays on, it usually means your system isn't detecting the graphics card. Start by turning off the PC, reseating the GPU, and checking that the power cables are firmly connected. Ensure your RAM is properly installed, try a different display cable or monitor, and update or reset the BIOS. If your CPU has integrated graphics, remove the GPU and test the system. If the light stays on, the GPU or motherboard may need professional diagnosis.