Why does the text in a ScreenGUI not change but it prints that it has changed?

I wrote a code to change the text of the ScreenGui according to the text on a SurfaceGui but it doesn't work

local buttonLeft = game.Workspace.Entries.LeftEnter --Part in the workspace
local leftValue = game.Workspace.LeftRoad.Truck.Value --BoolValue
local CounterLeft = game.Workspace.Counters.LeftCounter.SurfaceGui.Count
local LeftCountVal = game.Workspace.LeftRoad.Count --IntValue
local GuiCount = game:GetService("StarterGui").TruckEntered.PeopleTruck.PeopleNumber --textbox of the ScreenGui

if leftValue == true then --finding out if there is a vehicle on the left road
	local debounce = true
	buttonLeft.Touched:Connect(function(plr)
		if plr.Parent:FindFirstChild("Humanoid") then
			if debounce == true then
				LeftCountVal.Value = LeftCountVal.Value +1 --Value goes up
				debounce = false
				print(GuiCount.Text) -- prints "0"
				CounterLeft.Text = LeftCountVal.Value
				GuiCount.Text = CounterLeft.Text --text stays as 0
				print(GuiCount.Text) --prints"1"
				wait(0.5)
				debounce = true
			elseif debounce == false then
				LeftCountVal.Value = LeftCountVal.Value
			end
		end
	end)
end

The text on the ScreenGui stays as 0

The text that is printed goes up to 1

Now i changed it a little and an error pops up saying

18:38:26.094 - GetPlayerFromCharacter is not a valid member of Model

This is the new script

if leftValue == true then
	local debounce = true
	buttonLeft.Touched:Connect(function(hit)
		if hit.Parent:FindFirstChild("Humanoid")then
			if debounce == true then
				LeftCountVal.Value = LeftCountVal.Value +1
				debounce = false
				local player = hit.Parent:GetPlayerFromCharacter()
				player.PlayerGui.TruckEntered.PeopleTruck.PeopleNumber = LeftCountVal.Value
				CounterLeft.Text = LeftCountVal.Value
				wait(0.5)
				debounce = true
			elseif debounce == false then
				LeftCountVal.Value = LeftCountVal.Value
			end
		end
	end)
end

Btw this is in ServerScriptService What is the problem here?