My script work in the workspace, not in the StarterGui, what should I do?

I put a IntValue in the StarterGui and a script in the Value This is the script

script.Parent.Value = 3
wait(1)
script.Parent.Value = 2
wait(1)
script.Parent.Value = 1
wait(1)
script.Parent.Value = 5

The value is not changing when i play? What is the problem?