What does my TimeOfDay GUI work in studio mode but not in server mode?

So I have this day/night script and a GUI in my game that displays the TimeOfDay in a TextLabel. The day/night script works in both studio and server mode, but the GUI only works in studio mode - in server mode, the text remains as "08:00 am" despite the time passing.

Day/night script (server script placed in Workspace)

DAY_TIME_IN_MIN = 24 -- I set this to 24 so that each minute in game = 1 second real time

local dhour = 8 -- starts at 08:00
local dmin = 0
while true do
    wait(DAY_TIME_IN_MIN/24) 
    dmin = dmin + 1
    if dmin >= 60 then
        dmin = 0
        dhour = dhour + 1
        if dhour >= 24 then
            dhour = 0
        end
    end
    game.Lighting.TimeOfDay = dhour..":"..dmin
end

Script that updates the player's GUI according to TimeOfDay (server script placed in ServerScriptService)

game.ReplicatedStorage:WaitForChild("DayNight")

game.ReplicatedStorage.DayNight.OnServerEvent:connect(function(Player)
    print("started")
    while true do
        wait()
        if (tonumber(string.sub(game.Lighting.TimeOfDay,1,2))) == 12 then
            Player.PlayerGui.ScreenGui.Frame.TextLabel.Text =   
(tonumber(string.sub(game.Lighting.TimeOfDay, 1, 2))) .. 
string.sub(game.Lighting.TimeOfDay, 3, 5) .. " pm"
        elseif (tonumber(string.sub(game.Lighting.TimeOfDay,1,2))) == 00 then
            Player.PlayerGui.ScreenGui.Frame.TextLabel.Text = 
(tonumber(string.sub(game.Lighting.TimeOfDay, 1, 2)) + 12) ..                                                 
 string.sub(game.Lighting.TimeOfDay, 3, 5) .. " am"
        elseif (tonumber(string.sub(game.Lighting.TimeOfDay,1,2))) > 12 then
            Player.PlayerGui.ScreenGui.Frame.TextLabel.Text = 
(tonumber(string.sub(game.Lighting.TimeOfDay, 1, 2)) - 12) .. 
 string.sub(game.Lighting.TimeOfDay, 3, 5) .. " pm"
        elseif (tonumber(string.sub(game.Lighting.TimeOfDay,1,2))) < 12 then
            Player.PlayerGui.ScreenGui.Frame.TextLabel.Text = 
tonumber(string.sub(game.Lighting.TimeOfDay, 1, 2)) .. 
string.sub(game.Lighting.TimeOfDay, 3, 5) .." am"
        end
    end

end)

Script that fires a RemoteFunction called DayNight (this is a localscript placed in StarterGui)

game.ReplicatedStorage.DayNight:FireServer()

I tested the GUI script by adding

print("works")

in the GUI script when the event is fired, which the statement gets outputted in the server log -so I'm a bit confused why the TextLabel doesn't display TimeOfDay correctly...