Woops did some research on my own, you do have integrated. But it's a desktop and you can PROBABLY disable the Intel integrated GPU. Try thatUpdated extra information and tried older video drive... no dice (Hey, I noticed an Intel core, you got one with integrated graphics? Mabinogi won't see an Nvidia card if Intel HD graphics is also on board. It's been that way since... Well forever. I've had laptops with dual GPUs for most of my mabi career and this has been the issue time and time again.
It may be that you also seem to have two Nvidia GPUs in an SLI configuration, and that may be causing a hiccup.
For giggles, if you don't have an integrated GPU on your CPU and you are confident in your computer hardware skills (I assume you built the rig yourself but I could be wrong) try removing the second GPU/bridge and see if that stops the issue. Obviously this isn't a solution, merely a curiosity base venture to see if SLI configurations are unsupported...
Updated extra information and tried older video drive... no dice (Hey, I noticed an Intel core, you got one with integrated graphics? Mabinogi won't see an Nvidia card if Intel HD graphics is also on board. It's been that way since... Well forever. I've had laptops with dual GPUs for most of my mabi career and this has been the issue time and time again.