I'm going to wager it's because you don't have a monitor that reported it supports the resolution you're looking for by default. If you have a 4K monitor, you can add a custom resolution in the NVIDIA Control Panel under Display -> Change Resolution -> Customize... button. If you have something of lower resolution than the one you want, then you're going to have to enable DSR. However, keep in mind that DSR only works on set multiples. So divide the resolution you want by the monitor's resolution (just width or height will do) and see if that number shows up in the DSR factors list. If not, then you're just going to have to deal with the closest value.
Mikey101010 reacted to Mira Yurizaki in why has 1800p gone
