I have been playing Hbm ntm world on version [1.0.27_X4522]. I wanted to update the mod to version [1.0.27_X4895] when i did that everything was fine but jetpacks didn't work. All i did was replacing the old mod with new one in mods folder.

Check if the jetpack is fueled, it uses the correct fuel and that the jetpack is turned on via the "backpack" keybind.