PSTN callers get an "invalid conference id" message when joining a conference

Brian Hadfield -

When PSTN callers attempt to join a Lync conference they may receive an "invalid conference id" message and be denied access to the conference.  This can be caused by the Conference ID that is assigned in Lync being disassociated with the Lync account that is scheduling the conference.

To resolve this, the Lync user that scheduled the conference will need to reset their Assigned Conferencing Information.

To reset your Conferencing Information

  1. Close the Lync client by right-clicking on the Lync icon in the System Tray and selecting Exit.
  2. Close Outlook
  3. Open a browser and navigate to
  4. Login to the Dial-in Conferencing Settings and PIN Management page by providing your Lync credentials.



  1. After successfully authenticating, the Assigned Conference Information will be shown and a link to Reset my Assigned Conference information will be provided.  Click on that link to reset the conferencing information.


  1. After resetting your conferencing information, all new meetings should be scheduled with the new Conference ID.  Any existing meetings or recurring conferences will need to be updated to reflect the new Conference ID.

To validate the solution

  1. Open Lync
  2. Open Outlook
  3. Schedule a Lync conference
  4. Verify that the updated Conference ID is shown in the meeting request and verify that dialing-in to that conference via PSTN allows callers using the new Conference ID to join.



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  • Avatar
    Pearson Greer

    This worked for our user, but out of curiosity, what is the root cause for needing to do this? Were the prior values incorrect/out of date, or actually corrupted in some way?

  • Avatar
    Brian Hadfield

    Hi Pearson,

    This was an issue with the Conferencing ID not being properly updated when the SIP domain change was made for this particular user.  It appears that the value was properly updated for other users at the time of the change.

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