'Not a valid member of PlayerGui' when it is there?

I am making a script which, when a player touches a massive invisible 'zone block', it will change the zone name at the top of the screen in their UI. I've hit many hurdles with this, but my current one is just perplexing me. When touching the block this script is contained in, I recceive the error "TownName is not a valid member of PlayerGui", which simply isn't true, it is very much a child of PlayerGui at the time of the error. I've tried a few fixes such as a WaitForChild("TownName") function which seemed to give no output whatsoever and I really do not know what to try next.

local debounce = true


function onTouched(hit)

    local player = hit.Parent:findFirstChild("Humanoid")
    local char = game.Players:GetPlayerFromCharacter(hit.Parent)
    local tngui = char.PlayerGui.TownName.Background.Text
    local name = script.Value.Value

    if player == nil then return end
    if tngui.Text == name then return end

    if debounce == true then
    debounce = false
    tngui.Text = name

    wait(2)
    debounce = true

    end
    end

script.Parent.Touched:connect(onTouched)