iOS Question BLE scan & connect OK with iPhone 4S, but not with newer iPhones - why?

Private Sub Application_Start (Nav As NavigationController)
    NavControl = Nav
    Nav.NavigationBarVisible = False
    Page3.Initialize("Page3")
    Page3.RootPanel.LoadLayout("3")
    NavControl.ShowPage(Page3)
    csu.Initialize
    csu.CallSubDelayedPlus(Me, "AfterSplash", 2000)
 
    Page1.Initialize("Page1")
    Page1.RootPanel.LoadLayout("1")
'    Nav.NavigationBarVisible = True

    Page2.Initialize("Page2")
    Page2.RootPanel.LoadLayout("2")

    manager.Initialize("manager")
    ServiceId = UUID("FFE0")
    ReadChar = UUID("FFE1")
    WriteChar = UUID("FFE2")
    messagesToSend.Initialize
    SetState

    Set_up_page
 
    Timer1.Initialize("Timer1", 50) '1000ms = 1 second and data comes in at 2 Hz
    Timer1.Enabled = False
End Sub

Sub SetState
    btn_upload.Enabled = Connected
    btn_product.Enabled = Connected
    btn_get_settings.Enabled = Connected
    If Connected = False Then
        Connection_status.Color = Colors.RGB(255,0,0)
        Connection_status2.Color = Colors.RGB(255,0,0)
        Connection_status.TextColor = Colors.RGB(255,255,255)
        Connection_status2.TextColor = Colors.RGB(255,255,255)
        Connection_status.Text = "Not connected"
        Connection_status2.Text = "Not connected"
    End If
End Sub

Sub Manager_StateChanged (State As Int)
    If State <> manager.STATE_POWERED_ON Then
        hd.ProgressDialogHide
        hd.ToastMessageShow("Bluetooth is not enabled", True)
    Else
        StartScan
    End If
    SetState
End Sub

Private Sub StartScan
    Try
        Device_MAC = File.ReadString(File.DirDocuments,"MAC.txt")
    Catch
        Log(LastException.Message)
    End Try
    If manager.State = manager.STATE_POWERED_ON Then
        manager.Scan(Array())
    End If
End Sub

Private Sub Manager_DeviceFound (Name As String, DeviceId As String, AdvertisingData As Map, RSSI As Double)
    If Name.Length > 0 Then
    Log($"DeviceFound: ${Name}"$)
    For Each k As String In AdvertisingData.Keys
        Dim v As String = AdvertisingData.Get(k)
        Dim Index As String = v.IndexOf("FFE0") + v.IndexOf("4353")
        If Index = 5 Then
            If DeviceId = Device_MAC Then
                Enable_Connect = True
            End If
            If DevicesListView1.Size > 0 Then
                For I = 0 To DevicesListView1.Size-1
                    DI = DevicesListView1.GetValue (I)
                    If DeviceId = DI Then
                        Duplicate_Flag = 1
                    End If
                Next
            End If

            If Duplicate_Flag = 0 Then
                DevicesListView1.AddTextItem (Name, DeviceId)
                If Row_No < 39 Then
                    Row_No = Row_No + 1
                    Device_name(Row_No) = Name
                End If
            End If
            Duplicate_Flag = 0
            If Enable_Connect = True Then
                Enable_Connect = False
                Device_MAC = DeviceId
                Device_connect
            End If
        End If
    Next
    End If
End Sub

Private Sub Manager_Connected (Services As List)
    Log("Connected to " & Device)
    Connection_status.Text = "Connected to " & Device' & MAC
    Connection_status.Color = Colors.RGB(0,255,0)
    Connection_status.TextColor = Colors.RGB(0,0,0)
    Connection_status2.Text = "Connected to " & Device' & MAC
    Connection_status2.Color = Colors.RGB(0,255,0)
    Connection_status2.TextColor = Colors.RGB(0,0,0)
    Connected = True
    firstRead = True
    manager.ReadData(ServiceId) 'must call once to discover the characteristics
    SetState
    messagesToSend.Clear
'    Nav.NavigationBarVisible = True
    pnl_auto_connect.Visible = False
    NavControl.ShowPage(Page2)
'    btn_product_Click
    buffer = "#Prod" & CRLF
    Log(buffer)
    Dim msg() As Byte = buffer.GetBytes("UTF8")
    For I = 1 To 3
        SendMessage(msg)
    Next
End Sub

Private Sub Manager_DataAvailable (SId As String, Characteristics As Map)
    If firstRead Then
        manager.SetNotify(ServiceId, ReadChar, True)
        firstRead = False
        btn_product_Click
        Return
    End If
    Dim b() As Byte = Characteristics.Get(ReadChar)
    NewMessage(b)
End Sub

Sub SendMessage (msg() As Byte)
    Try
        manager.WriteDataWithResponse(ServiceId, WriteChar, msg)
    Catch
        Log(LastException)
    End Try
End Sub

Private Sub Manager_WriteComplete (Characteristic As String, Status As Int)
    If Connected = False Or messagesToSend.Size = 0 Then Return
    messagesToSend.RemoveAt(0)
    If messagesToSend.Size > 0 Then
        Try
            manager.WriteDataWithResponse(ServiceId, WriteChar, messagesToSend.Get(0))
        Catch
            hd.ToastMessageShow("Device is disconnected", True)
            Log(LastException)
        End Try
    End If
End Sub

Private Sub Save_Device_MAC
    Try
        File.WriteString(File.DirDocuments,"MAC.txt",Device_MAC)
'        Log("We are Inactive" & TAB & modFun.Today & TAB & modFun.Now )
    Catch
        Log("Did not save " & LastException.description)
'        modFun.ShowError("Main_Application_Inactive " & LastException.description)
    End Try
End Sub

Private Sub Manager_Disconnected
    Connected = False
    SetState
    StartScan
End Sub