Have you checked in the bios to make sure it's set to prioritize the GPU output first and not the IGPU? Sometimes the bios is set to the Integrated GPU on the CPU which the 7800X3D has. Do you get video if you connect your cable to the motherboard graphics output? If you do, my guess is that it's prioritizing the IGPU. You'd have to go into the bios and change the settings to GPU first and/or disable the IGPU
Ryzen 7800X3D - Radeon 7900XTX - MSI Tomahawk X670e MB - 64gb 6000mhz G-Skill Neo - Noctua NH D15 - Seasonic Focus V3 GX-1000W PSU - 4TB Samsung Gen. 5 NVMe - Fractal Torrent Case - ROG PG48UQ OLED