Why wont my Chatbox work?

I have been making a new chat interface, but for some reason it all falls apart when I test it with more players:

script.Parent.Focused:connect(function()
    if script.Parent.Text == "Press T, /, or click here to chat" then
        script.Parent.Text = ""
    end
end)
script.Parent.FocusLost:connect(function(EnterPressed)
    if EnterPressed and script.Parent.Text ~= "" then
        script.Parent.Parent.Value.Value = script.Parent.Text
        script.Parent.Text = "Press T, /, or click here to chat"
    end
end)
function onKeyPress(inputObject, gameProcessedEvent)
    if inputObject.KeyCode == Enum.KeyCode.Slash or inputObject.KeyCode == Enum.KeyCode.T then
        script.Parent:CaptureFocus()
    end
end
game:GetService("UserInputService").InputBegan:connect(onKeyPress)

There are NO output errors, so please dont ask