Hello @Marc ,
Recent Updates on this case as posted here: From Microsoft Product Support Team
Can you please confirm that you are sending data?
If you are sending data, can you double-check if you created any Route in IoT Hub? We read data from the built-in endpoint, but when you create a Route, by default IoT Hub stops sending data to that endpoint: Understand Azure IoT Hub message routing | Microsoft Learn. If you are using routes, you need to make sure you are sending data to the built-in endpoint:
"Built-in endpoint as a routing endpoint"
You can use standard Event Hubs integration and SDKs to receive device-to-cloud messages from the built-in endpoint (messages/events). Once a Route is created, data stops flowing to the built-in-endpoint unless a Route is created to that endpoint."
Please comment in the below section for further discussion in this matter.