Why do I see a common module flow validation error?

In an inbound call flow that uses the Call Common Module action to call a common module, you may encounter a validation error. This validation error appears in the call flow, indicating that the common module contains errors that must be fixed. However, when you open the common module flow, no validation errors appear and you can publish the flow.

This validation error can occur when the common module uses text-to-speech or speech-recognition functionality, and requires that the flow has a configured text-to-speech engine for all languages supported by the common module flow. Because the calling flow sources the data needed for such functionality in the common flow, the calling flow must have the same set of supported and configured languages.