Enabling Accessibility service.

To read system notifications (for instance Notification.asUpdates()), you need to enable notification service by setting notification_enabled value to true in resource XML.

Specifically, in res/values/bools.xml (create one if not exist), add the following line(s):

<resources>
    <item name="notification_enabled" type="bool" format="boolean">false</item>
    ...
</resources>