No option for 3840x2160 resolution unless fullscreen

My game was working fine but I recently dual boxed for the first time and now it’s all messed up. I have one monitor that’s 4k (3840x2160) and another that is 1920x1080. When I launch the game, it opens up on the 4K monitor but it does not take up the full screen. I when I try to change the resolution, there is no option for 3840x2160, UNLESS I set it to full screen.

How do I get it to become 4K resolution while in fixed window?

dude this is so glitchy. I closed out of the game while it was in full screen mode and in the correct resolution (3840x2160). I then re-launched the game and tried setting it to fixed window mode, also 3840x2160 resolution (which now appeared as an option). But when I hit apply, it switched to 3840x1603 resolution. I cannot for the life of me get eve back to the correct resolution.

Problem solved! I fiddled around with the UI Scaling in windows and inadvertently got Eve into a 2560x1440p resolution and filling the whole screen. It could be my eyes, but the image quality doesn’t have the same level of crispness as it did in 4K, but it’s playable now and this is what it looked like before I got it all messed up from dual boxing. Hopefully this will help someone in the future who may have the same problem. Also, maybe this could be made more intuitive for future people who are brain poor like me to figure out how to resolve.