Hey! So there’s actually two things going wrong here.
First, quick typo - you’re passing true instead of false in your pcall, so you’re literally just enabling it over and over lol.
But even if you fix that, it still probably won’t work - SetCore("TopbarEnabled") is busted with Roblox’s new CoreGui. There’s an open bug report on the devforum from late 2024 and it’s still not fixed as of this year. So all those old posts from 2020 aren’t going to help you unfortunately.
What actually works right now is SetCoreGuiEnabled. Swap your script out for this:
local StarterGui = game:GetService("StarterGui")
while not pcall(function()
StarterGui:SetCoreGuiEnabled(Enum.CoreGuiType.All, false)
end) do
task.wait()
end