local checkpoints = game.Players.LocalPlayer:WaitForChild("Checkpoints")
Unlocked200 = checkpoints.Unlocked200
local M200 = script.Parent
while true do
wait(0.01)
if Unlocked200 == true then
M200.Visible = true
end
end
Unlocked200 is a bool value, even when the value is true, the Button is still invisible.

3 comments
change Unlocked200 == true to Unlocked200.Value == true
also, according to me shouldnt use numbers in your names
says by HKG_7551