Azure Communication Services Speech Recognition Fails with Code 408 - Cognitive Services Timeout

Question

I'm currently working with Azure Communication Services (ACS) Call Automation and facing an issue where speech recognition repeatedly fails with a 408 status code during live calls.

Important Context:

This service has been running successfully for 6–8 months, without any code changes on our end. The issue started happening recently, and no infrastructure changes were made either.

Setup Summary:

• I'm using azsdk-python-communication-callautomation==1.2.0
• Cognitive Services endpoint is linked and configured for speech recognition.
• Prompt is played using TextSource, and start_recognizing_media() is used with:
• RecognizeInputType.SPEECH,

initial_silence_timeout=15,

end_silence_timeout=0.3,

interrupt_prompt=True

• Everything is running in a FastAPI server and using the ACS callback events. Issue Details: The recognition fails silently with the following log:

    WARNING - Recognition failed for call [ID]. Error: No error message  
  

Message: Action failed due to a request to Cognitive Services timing out. Please try again later or check for any issues with the service.
SubCode: 8565

  
  The ACS call logs show that the recognition request is **accepted (202)** and the task is **initiated**, but eventually it times out and triggers a `Microsoft.Communication.RecognizeFailed` event. Immediately after, the call disconnects.
  
  Here’s a snippet from the logs:
  
  yaml
  POST /api/callbacks HTTP/1.1" 200 OK  
...  
Recognition failed. Code: 408, Message: Action failed due to a request to Cognitive Services timing out...  
...  
Call disconnected for call ...