Password Accessable Gui (Keys Table) only working with one value in table! [help plz?]

I wrote the code that you have, and I see the problem. I dunno if this is a common problem or not. But this code should work

local Keys = {"Key1", "Key2", "Key3"}

script.Parent.MouseButton1Down:Connect(function()
	for _, Key in pairs(Keys) do
		if script.Parent.Parent.TextBox.Text == Key then
	       		script.Parent.Parent.OutputBox.Text = "Key activated successfully!"
			return
	    end
	end

	script.Parent.Parent.OutputBox.Text = "Incorrect key, please try again!"
end)

The problem of your code is the if statement. It's hard to explain so I'll try my best

For example... You're input was "Key2", so it would iterate over the Keys table, so when it iterates the first element the for loop is going to see is "Key1", so in the if statement, the result will be

if "Key2" == "Key1" then

because of that it would run the else statement instead, and only run the code when it iterates through "Key2".

So in the code that I wrote, it would iterate through as usual and if it's not the correct key it wouldn't do anything, if it does find the correct one it would run the code inside the if statement and returns (return makes the code after it not run). If it's not the correct key and it finished iterating, it would stop the for loop and run the "Incorrect key" code.

So I hope I did a pretty good explanation, cause I ain't good at doing one.