How do I make a player do a cannon ball?

I added a button in my game and when you click it, you will be launched forwards and the player will sit. In the button I have this script:

local button = script.Parent
local boing = button.Boing -- Sound Effect
local cannonBall = game.ReplicatedStorage.CannonBall
local d = false

button.MouseButton1Click:Connect(function()
    if d then return end

    button.Boing:Play() -- Boing Sound plays

    cannonBall:FireServer() -- The Script that makes the player launch forwards starts

    d = true

    wait(2.5) -- delay

    d = false
end)

Here is the Launch script inside StarterCharacterScripts:

local cannonBall = game.ReplicatedStorage.CannonBall
local char = script.Parent

cannonBall.OnServerEvent:Connect(function()
    local hum = char.Humanoid
    local HRP = char.HumanoidRootPart

    hum.Jump = true

    wait(0.2)

    HRP.Velocity = HRP.CFrame.LookVector * 100

    hum.Sit = true
end)

Whenever I click the button, I do jump in the air and sit, but I never get launched forwards. For some reason, the velocity thing isn't working. Please tell me why.

Thx to the people who will help! :)