xamarin update label and progress bars been killed by change to a different activity (need a fix)

We have a very simple app which reads data over a Bluetooth connection and updates a text string on a page. All the updates work as normal via the timer, but when we switch to a different page in the app and return to the home page, the updates stop working. We can set a break point on the text string update and we can see the new value but it does not update. Why when we change to a different page and returns does it's stops the updates? It's a simple label and it's been updated in the UI? I would like to understand how to fix this problem using System; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; using [login to view URL]; namespace Custom_TestAppHarness { [XamlCompilation([login to view URL])] public partial class Homepage : ContentPage, INotifyPropertyChanged { public Homepage() { InitializeComponent(); // Start timer to update all the information on the home activity if (App._timeerhasstarted == false) { App._timeerhasstarted = true; [login to view URL]([login to view URL](5), () => { [login to view URL](() => { testcall(); }); return true; //use this to run continuously }); } } void testcall() { [login to view URL](async () => { [login to view URL] = [login to view URL](); [login to view URL] = App._vehiclefuellevel; [login to view URL] = App._vehiclebatterylevel; }); } protected override void OnAppearing() { [login to view URL](); [login to view URL] = [login to view URL](); } } } XML code for the label <Label x:Name = "BTTextStatus" Grid.Row="2" Grid.Column="0" Grid.ColumnSpan="6" HorizontalOptions="CenterAndExpand" VerticalOptions="CenterAndExpand" TextColor="#cccccc" FontSize="Medium"/>