This article provides information on the most common root cause when experiencing an integration issue when using a Skype enabled On Demand account.
Once it has been confirmed that the audio details in the O365 portal are correct the information below should be provided to the client regarding the bar bell connection issue that is the leading root cause of integration issues.
All users need to be ensuring that they are using the three dots at the bottom right hand side of the screen to choose "End Meeting" in the Skype meeting window instead of using the "X" in the top right hand side of the screen to close the window. Using the "X" causes an issue with the bar bell connection on the backend. The barbell connection is what enables the integration of the audio in Skype for Business meetings and when it has become corrupted Skype audio and conference bridge participants are unable to hear each other. Opening a new meeting and closing it properly can correct the issue going forward and is a best practice.
If this is unsuccessful and integration settings have been confirmed correct the next step is to escalate to the appropriate Provider.