https://learn.microsoft.com/en-us/uwp/api/windows.services.store.storecontext.offlinelicenseschanged?view=winrt-28000
StoreContext.OfflineLicensesChanged Event (Windows.Services.Store) - Windows apps | Microsoft Learn
Raised when the status of the app's license changes (for example, the trial period has expired or the user has purchased the full version of the app).
windows serviceseventstoreappsmicrosoft