How to handle Toasts (App Notifications) across multiple instances of app?

[eFail]

I followed the instructions here to enable Toast support in my multi-instance application.

When each instance of my app gets launched, it uses AppNotificationManager to register for Toast notification events:

AppNotificationManager.Default.NotificationInvoked += AppNotificationManager_NotificationInvoked;
AppNotificationManager.Default.Register();

void AppNotificationManager_NotificationInvoked(object sender, AppNotificationActivatedEventArgs args)
{
    // Does nothing yet.
}

Each instance of my application launches MainWindow which has one button that generates a toast when clicked.

When I press the button on the first instance (ProcessID=1) of my app and then click on the generated Toast, the AppNotificationManager_NotificationInvoked handler gets called as expected.

If I launch a second instance of my app (ProcessID=2) and do the same thing, AppNotificationManager_NotificationInvoked gets called again, but instead of being called for the second instance of my application, it gets called for the first instance (PID=1).

It seems that no matter how many independent instances of my application get launched and register for toast notifications, only the first instance ever receives the notifications.

I took a look at this article on App Lifecycle Instancing, hoping that it may provide a way to send a NotificationInvoked event from one instance to another, but since the Toast notifications don't come in through AppInstance.GetCurrent().Activated, I can't see a way to do it.

Am I missing something here. Windows App SDK applications are mult-instance by default. And to that point, what I want is for each instance of my application to independently manage activation of toasts that it generates. How can I accomplish this?

Thanks in advance?