Why wont this script thats meant to print when the health is zero work?

Your script probably only runs once, that’s why. You can use a loop or function to fix this. Here’s some examples :

Loop :

Health = script.Parent.Humanoid.Health
Head = script.parent.Head
Eye1 = script.Parent.Eye1
Eye2 = script.parent.Eye2

while wait() do

if Health <= 0 then
print("Hello world!")
end

end

Loops will constantly run the code that is in the loop, but that also means it will not run any code under it until the loop ends/breaks.

Function :

Humanoid = script.Parent.Humanoid
Head = script.parent.Head
Eye1 = script.Parent.Eye1
Eye2 = script.parent.Eye2

Humanoid:GetPropertyChangedSignal(“Health”):Connect(function()
if Humanoid.Health <= 0
then print("Hello world!")
end

I prefer functions more as code can still run through the functions instead of stalling at it. This function will run once the health property in the humanoid changes.

Hope this helped!

Also why are you using > ? That makes the conditional statement run only if the health is greater than 0 (Ex: 1, 3, 100, etc.). I changed it to < = so the code will run only if the health is below or equal to 0.