After creating a subscription in the Pub/Sub service, you need to open the developer console and register the created topic as a target for RTDN (Real-time developer notifications). To do this, go to the app’s Monetization Setup section and enter the full name of the topic in the Topic name field. After that, send a test notification using the link below. If everything is configured correctly, then the test notification will change the integration status of the subscription in devtodev to Active.