Lync Troubleshooting: Conferencing Error

Symptoms

While scheduling or joining a Lync meeting, you see the message "Conferencing Error."

Resolution

If you run into issues scheduling or joining an online meeting or conference call, contact your support team. To help them resolve the issue, check the following:

Specify which application you are using for conferencing (for example, Lync or Lync Web App).
Make sure your phone or device is optimized for conferencing. A list of devices that are optimized for Lync is available on Microsoft TechNet at Phones and Devices Qualified for Microsoft Lync.
Specify which version of Lync or Communicator you and your participants are using. Some newer versions may not support or operate the same way as older versions.
Test your audio device(s) from the Options dialog box and confirm that they are functioning properly before trying the conference again.
Have participants confirm with their support teams that their networks and accounts support conferencing.
Try to send an instant message to one contact first, then add voice to the conversation, then add a third person to start a conference. It helps your support team to isolate the issue if you can specify which functions are working and which are not. If instant messaging and peer-to-peer communication function without issues but conferencing fails, then contact your support team to ensure that the network routes and ports to the conferencing server are not blocked.
If you are having issues with scheduling an online meeting or conference call, try to join a different online meeting or conference call first. Or if you are having issues with joining, try scheduling. It helps your support team if you can isolate the issue as having to do with scheduling or joining.
If you are having issues with scheduling or joining conferences in Lync 2010, try joining by dialing-in with a phone, or using Outlook to access and open the meeting invitation. It helps your support team to isolate the issue if you can specify which forms of access are functioning and which are not.
If you are having issues with scheduling or joining, see if others can schedule and join conference calls. If no one can schedule or join conference calls, then the issue is likely related to network connectivity (for example, there may be an intermittent issue or temporary network outage).
If you are conferencing with external contacts, contact your support team to make sure that your account is enterprise voice (EV) enabled.