COMException (0x80070490) when subscribing to UserNotificationListener.NotificationChanged in unpackaged WinUI 3 app

[koiseka]

Describe the bug

In an unpackaged, self-contained WinUI application, subscribing to UserNotificationListener.NotificationChanged throws a COMException with HRESULT 0x80070490 (Element not found).

Other UserNotificationListener APIs appear to function correctly in the same scenario. Specifically:

• UserNotificationListener.Current
• RequestAccessAsync() returns Allowed
• GetNotificationsAsync() works as expected

However, attempting to register the NotificationChanged event consistently fails at runtime.

Repro project

https://github.com/koiseka/notificationchangedexample-repro

Steps to reproduce the bug

1. Clone the repro project: https://github.com/koiseka/notificationchangedexample-repro
2. Open NotificationChangedExample.sln in Visual Studio
3. Build and run the app (unpackaged, self-contained)
4. App calls RequestAccessAsync() → returns Allowed
5. Subscribing to UserNotificationListener.NotificationChanged throws COMException (0x80070490)

Expected behavior

The NotificationChanged event should either:

• Successfully subscribe and fire when notifications change, or
• Fail with a clear, documented error indicating that the API is unsupported for unpackaged apps

Screenshots

No response

NuGet package version

Windows App SDK 1.8.4: 1.8.260101001

Packaging type

Unpackaged

Windows version

Windows 11 version 24H2 (26100, June 2025 Update)

IDE

Visual Studio 2022

Additional context

Failing call

listener.NotificationChanged += Listener_NotificationChanged;

Throws immediately with:

System.Runtime.InteropServices.COMException (0x80070490): Element not found
   at ABI.WinRT.Interop.EventSource`1.Subscribe(TDelegate handler)
   at Windows.UI.Notifications.Management.UserNotificationListener.add_NotificationChanged(...)

[riverar]

Can confirm this API will let you spin up an instance of UserNotificationListener no problem, and even return OK via RequestAccessAsync but fail when trying to wire up events. Apps with identity appear to work fine (as those go through capability manager, et al.).

Is this API supported in unpackaged scenarios? @DrusTheAxe @jonwis