This is my script, aimed to prevent your character from being able to jump. It is in workspace.
local h=script.Parent:WaitForChild("Humanoid") h.Changed:connect(function(p) if p=="Jump"then h[p]=false end end)
That won't work. Jump will immediately be set to false after jumping anyway (look at the property window of the humanoid and jump, you'll see.)
Have you tried setting JumpPower to 0?
you put == instead of = on line 3