Why requestaccessasync gives denied by system in phonelinetransportdevice windows

DeviceInformationCollection devices = await DeviceInformation.FindAllAsync(PhoneLineTransportDevice.GetDeviceSelector(PhoneLineTransport.Bluetooth));
for (int i = 0; i < devices.Count; i++)
{
    Console.WriteLine(i + "#:    " + devices[i].Name + "    " + devices[i].Id);
}

select:
Console.WriteLine("Please input device id to select");

if (int.TryParse(Console.ReadLine(), out int s))
{
    if (s < 0 || s > devices.Count)
    {
        goto select;
    }
    Console.WriteLine("Selected: " + devices[s].Name + "    " + devices[s].Id);
}
else
{
    goto select;
}

var PDevice = PhoneLineTransportDevice.FromId(devices[s].Id);
var result = await PDevice.RequestAccessAsync();
if (!PDevice.IsRegistered())
{
    PDevice.RegisterApp();
}
var flag = await PDevice.ConnectAsync();
if (flag)
{
    Console.WriteLine("Connected");
}
else
{
    Console.WriteLine("Could not connect to PhoneLineDevice");
}
PhoneCallStore store = await PhoneCallManager.RequestStoreAsync();
PhoneLine pl = await PhoneLine.FromIdAsync(await store.GetDefaultLineAsync());
pl.DialWithOptions(new PhoneDialOptions { AudioEndpoint = PhoneAudioRoutingEndpoint.Bluetooth, Number = "18589846271" });

Console.ReadLine();
PDevice.UnregisterApp();