Help with suddenly undeteced GPU please

So I have been running the following rig for 4-5 months with zero issues: msi z390a pro mobo, 6 x msi 1660S, ubit risers, intel i5 gen 8 w/ integrated graphics, 16gb corsair 3200mhz RAM, 1000w platinum rated corsair psu. Yesterday at work I was monitoring my rig remotely and noticed that T-rex miner said I had a gpu idle. When I got home I saw that no updates had taken place and nothing had changed in my settings and there were no errors reported. However, my 5th gpu had it's rgb lights on, but was not synced with the others rgb (I know it's a waste of power, but they are only on while awake) and not detected by msi afterburner, mystic lights, gpuZ, etc. What causes a computer to suddenly stop recognizing a gpu when seemingly nothing has changed? My temps never go above 55C and there is adequate ventillation, little to no dust, and humidity that never goes above 40%.

Edit: Running windows 10

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Things I tried: Swapped the pcie riser for a brand new one. Tried swapping pcie slots on the mobo (other gpus work in the 5th slot, but the one that was originally in the 5th slot is not detected when plugged into the other slots) swapped the power cable out, downloaded the latest NVIDIA drivers for this GPU, tried just plugging this gpu into the first slot by itself with no other gpus and it is still not deteced. It recieves power as the rgb lights illuminate. Any ideas or advice? I'm reluctant to do a clean wipe and reinstall everything, but I will as a last "why not" though.

Any help is greatly appreciated!