TextLabel doesn't update?

I've run into this problem a lot of times with games I've made, the #1 solution I have found was to put a StringValue into Lighting and name it "Alert" and do the following

Script that changes the text:

    local alert = game.Lighting.Alert
    alert.Text = "Test String"
    wait(2)
    alert.Text = "Test #2"

Script Inside the TextLabel:

    local alert = game.Lighting.Alert
    update = function()
        script.Parent.Text = alert.Value
    end
    update()

    alert.Changed:connect(update)

for i,v in pairs(game.Players:GetChildren()) do
v.PlayerGui.GUIAndLocationHere
end

This code will loop through all the players currently in the game and execute the action per player.

Rather than iterating through each player, I'd have a script inside each GUI that updates the TextLabel when the number of players changes. If I was you, this is what I'd have-

local Label = script.Parent
local Players = Game:GetService("Players")

function update()
    Label.Text = Players.NumPlayers .. " players"
end

Players.Changed:connect(function(property)
    if property == "NumPlayers" then
        update()
    end
end)