Radius script works in studio but not in a server. Can someone help me?

I have a script that when you walk into the zombies radius it shows his health (health is in another script) but the radius script works when i'm in studio but not in a server, please help D:

local Player = game.Players.LocalPlayer.Character
local Zombie = game.Workspace.Zombie

while wait() do
    if (Player.Torso.Position - Zombie.Torso.Position).magnitude <= 30 then
        script.Parent.BOSS.Frame.Visible = true
    else script.Parent.BOSS.Frame.Visible = false
    end
end