Try dropping it to the lower x16 slot, clear CMOS, and plug everything back in with the monitor connected to the GPU. 
This morning my graphics card (GTX 1660 Ti) is no longer being detected by the computer.  When I go to the device manager, I can see it when I show hidden devices, but is showing a Code 45 error (currently, this hardware device is not connected to the computer).  I can see the the gpu's fan is still running. I've updated the bios to the latest version, but I can't install new NVidia drivers as it doesn't detect a compatible device.  I don't know why it would have suddenly become disconnected as I haven't moved the computer at all recently.  Is there another possible problem, or should I look into removing and reconnecting the card? Many thanks!
Aurora R8, GTX 1660 Ti no longer detected