I downloaded driver version 425.31 from Nvidia's site, modified the nvdmi.inf, and enabled test mode to bypass the driver signature. When I run the installer, it says "Nvidia graphics driver is not compatible with this version of Windows." I am running 1809 but I don't expect that to be the issue since this error didn't happen for other cards on other machines running the same version. This is a fresh install too. The only other clue I have is that Device Manager has a warning on one of the cards but I assumed it's because the Windows basic driver can't handle SLI. The cards previously both worked in an R2. My next move I think is to pull the secondary and install for the single card before popping the second back in. I'd like to avoid disassembling this more than necessary though since some of the mobo headers have loose clamps and it's a huge pain getting it back together. Any other ideas?