What are two possible causes of the issue?

You have 1,000 devices that connect to a standard tier Azure IoT hub.

All the devices are commissioned and send telemetry events to the built-in IoT Hub endpoint. You configure message enrichment on the events endpoint and set the enrichment value to $twin.tags.ipV4.

When you inspect messages on the events endpoint, you discover that all the messages are stamped with a string of "$twin.tags.ipV4".

What are two possible causes of the issue? Each Answer presents a complete solution. NOTE: Each correct selection is worth one point.
A . The ipV4 tag is a restricted twin property that is unavailable for message enrichment.
B . A standard tier IoT hub does not support device twin properties in message enrichments.
C . The device sending the message has no device twin.
D . Message enrichment cannot be added to messages going to a built-in endpoint.
E . The device twin path used for the value of the enrichment does not exist.
F . The device twin property value used for message enrichment is set to "$twin.tags.ipV4".

View Answer

Answer: C,E

Explanation:

In some cases, if you are applying an enrichment with a value set to a tag or property in the device twin, the value will be stamped as a string value. For example, if an enrichment value is set to $twin.tags.field, the messages will be stamped with the string "$twin.tags.field" rather than the value of that field from the twin.

This happens in the following cases:

(C) Your IoT Hub is in the standard tier, but the device sending the message has no device twin.

(E) Your IoT Hub is in the standard tier, but the device twin path used for the value of the enrichment does not exist. For example, if the enrichment value is set to $twin.tags.location, and the device twin does not have a location property under tags, the message is stamped with the string "$twin.tags.location".

Your IoT Hub is in the basic tier. Basic tier IoT hubs do not support device twins.

Reference: https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-message-enrichments-overview