Click to attack script doesn't work, for some reason it just stops?

Hello! I was trying to create a click to attack script which plays an animation on click. When I made the script, the only thing that didn't seem to work was the function at the bottom of the script. I took it from a tutorial, so I have no idea at all how to fix it. By the way, I'm not using a tool. I'm using an accessory with a union that has an attachment in ServerStorage.

userInputService = game:GetService("UserInputService")
print("1")
storage = game:GetService("ServerStorage")
print("1")
scissor = storage.ScissorBlade
print("1")
plr = script.Parent.Parent.Character
print("1")
animation = plr.Humanoid:LoadAnimation(scissor.Animation)
print("1")

userInputService.InputBegan:Connect(function(input, gameProcessedEvent)
    if input.UserInputType == Enum.UserInputType.MouseButton1 then
        print("Attack")
        plr.Humanoid.WalkSpeed = 0
        animation:Play()
    end
end)

Those print("1")s were tests to see if the problem was from any of the variables; all 1s printed successfully. Also, "Attack" did not print. If anyone knows how to fix or make this script better, please write an answer, and thank you!