I had 2560x1440 120hz available as option in Windows 10 but since the latest firmware update the option is no longer there. 1080 at 120hz as well as 4k at 60hz work just like before, but that mode especially is gone from the options.
Further specs are hdmi 2.1 cable and Nvidia gzx1070.
I hope there is a way to fix this now or maybe address this issue with an upcoming firmware update?
I had the same problem and it was extremely annoying. Fortunately I was able to use the Nvidia Control Panel to force 2560x1440 120hz.
I'm not at my pc right now, so might be hard for me to guide you but go to the resolution area in the Nvidia Control Panel, there you should be able to do a custom display setting. For the custom setting select 2560x1440 120hz and save it. Once saved that custom setting will be at the very top of the list of resolutions. It works perfectly for me.
Thanks for the suggestion, I am not quite sure this is working as intended though. I can set up a custom resolution for that mode, but checking in windows the actual output setting still seems to be 1440p 59 hz or 1080p 120hz.
I had the same problem. Sometimes NVIDIA recognized 1440p@120Hz resolution.
In the NVIDIA Control Panel, I've added custom resolution 2560x1440@120Hz with automatic scan then I switched to it. Now it works like a charm