Yeah one of the first thing I tried is plugging only those not-detected GPUs one at a time but both are not getting recognized by Windows 10 Pro (64 bits). I've tried to put those GPUs into my other rig but my other rig doesn't detect them also. I am running Windows 10 Pro (64 bits), the OS only detects 3 GPUs out of 5.
When I was placing those GPUs on the motherboard the power supply was always turned off to avoid a shock. Something that makes me ask myself some questions is that those 2 GPUs when I am booting, their fans are running OK and all lights are on the GPUs and the LED light on the PCI-e risers are on also....
Thanks
If you tried them one at a time and windows 10 didn't recognize them does that mean that your bios recognized that card resp. you saw the boot screen when a monitor was plugged in? If you can't see the post messages or enter the bios, don't even bother with the cards, they are most likely gone and you only can replace them.