game.Workspace.checkpoint1.Changed:connect(function() --This is an event listener, it triggers a function.
if game.Workspace.checkpoint1.Transparency == 1 then
script.Parent.GUI1.Visible = false
end
end)
Doesn't work. When checkpoint1, a part in workspace, disappears, it's supposed to also disappear gui1. but it won't work. Why won't it make GUI1 invisible when checkpoint 1 disappears?
It's in a local script in GUI. The script that actually turns the brick invisible is in ServerScriptStorage and works fine.

2 comments
I set up your description of the circumstance in my Studio, and it worked fine. Is GUI1 a GuiObject? Also, are there any errors that go into the output when you test it?
GUI1 is a ScreenGUI with a text label. No errors.