What troubleshooting steps can I take to identify the cause of my GPU not being detected in my PC, considering that I rely on it for daily work and cannot take the entire rig to a repair shop? My PC specs include an Intel Core i5 10th gen, an RTX 2060 GPU, a Corsair 550W PSU, an Asrock B460M motherboard, and a decent UPS. I have already tried updating/reinstalling drivers, reseating the GPU, upgrading the BIOS, and the GPU functions without issues when tested on a different board. What could be the potential causes, starting from the least severe to the most severe, such as motherboard, PSU, or connector issues?