# Debugging unexpected hangups in the Amazon Chime SDK PTSN audio service
<a name="unexpected-hangups"></a>

Complete the following troubleshooting actions if you experience unexpected hangups or error messages with AWS Lambda functions for the PSTN audio service:
+ Verify that your AWS Lambda policy grants the `lambda:InvokeFunction` permission to the [voiceconnector.chime.amazonaws.com](http://voiceconnector.chime.amazonaws.com/) service principal.
+ Check the logs for your AWS Lambda function to ensure that it's being successfully invoked.
+ If the logs show incoming events and returned actions, verify that you don't return a hangup action in when the AWS Lambda function is invoked.
+ Check the CloudWatch logs for your SIP media application. The following table lists some of the messages you may encounter.    
[\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/chime-sdk/latest/dg/unexpected-hangups.html)