I was using better UI, and when I disabled it, my jumping came back. I'll try disabling the xp bar, because I really like better UI. Thanks.

assuming your running mods, your probably using better ui mod, and its breaks jumping, you can fix it by disabling 'show character xp bar' in the settings menu for better ui

I've noticed that you jump a lot better if you are holding sprint as well. Even if you're not actually running anywhere, like just trying to get up a single block height, I'll fall just short when jumping normally, but make it when I'm holding sprint while jumping.

I think it was somekind of UI mod that caused this. Remove it and you can jump again. Not game's fault.

I can jump just fine. Not sure what your issue may be. Has the jump key (space by default) been unbound for you for whatever reason?

Obviously, though, jumping is limited by both Stamina and your Jump skill.

provide details... jumping works as always for me (no mods here).

Only time I couldnt jump was when I tried out some mods. Cant remember what mod it was that caused it for me though.