Cannon script, wont work? ball wont even show up

I think this might fix the problem:

local Cannon = game.workspace.Cannon
local sp= script.Parent
local Action=sp:WaitForChild("ClickDetector")

function FireCannon()
    local Ball = Instance.new("Part", game.Workspace)
    Ball.Name = "Effect"
    Ball.Shape= "Ball"
    Ball.Material= "Concrete"
    Ball.Size=Vector3.new(3,3,3)
    Ball.CanCollide=false
    Ball.CFrame = Cannon.CFrame
    Ball.Velocity = Cannon.CFrame.lookVector*50 --You might want to make this a larger number
    Ball.TopSurface="Smooth"
    Ball.BottomSurface="Smooth"
    Ball.Position = Cannon.Position
    Ball.Touched:connect(function(Part)
        if Part~=Cannon then
            local Ex=Instance.new("Explosion",game.Workspace)
            Ex.Position=Ball.Position
            Ball:remove()
        end
    end)
end

Action.MouseClick:connect (FireCannon)

while true do --Remove this "while" loop if you want it to only fire when you click the part.
    wait()
    FireCannon()
end

Ok, so you basically had a lot of minor spelling errors. I think I should have fixed all or most of it. Make sure that there is a ClickDetector inside of the scripts parent, and that it's name is "action". Make sure that there is also a "Cannon" in the Workspace. If you have done all of this correctly, then it should work (I tested it also)

Also, I've added this little bit of code I think might help a bit with what your trying to accomplish:

Ball.Touched:connect(function(Part)
    if Part~=Cannon then
        local Ex=Instance.new("Explosion",game.Workspace)
        Ex.Position=Ball.Position
        Ball:remove()
    end
end)

This basically just finds when the ball was hit by anything besides the cannon, then makes an explosion and removes the ball. If you do want to add it, add it in at the end of the FireCannon() function that you have. It should work fine.

Anyways, if you have any problems or questions, please leave a comment below. Hope I helped :P