Cloud Computing Support Image

Skype for Business Troubleshooting

Resolve Skype for Business connectivity and sign-in issues.


Last Review: January 4, 2016

Product(s): Office 365, Skype for Business

Office 365 Support

In order to provide support, make Matrixforce your Office 365 Partner at no cost.

Office 365 Partner of Record 277554


The Office 365 DNS setup must be completed. A valid Skype for Business license muste be assigned in the Office 365 Admin Portal and the latest version of Skype for Business should be installed.

  1. Make sure that your computer clock is set to the correct time because Skype uses a timestamp as part of the authentication process. If the time is more than 5 minutes off, you will not be able to sign-in and should correct the time and try to sign-in again.
  2. Next try the Office 365 Skype setup for manual configuration:
    1. Click the Settings icon in the upper-right, Tools, then Options.
    2. Click Personal and the Advanced button.
    3. Enter as the Internal and External server under Manual configuration.
    4. Click OK twice and try to sign-in again.

If the above fails, then follow the steps below:

  1. Exit the Skype client completely. Ensure that it is not still running in the system tray.
  2. Open an administrative command prompt, type the following, and hit enter: ipconfig /flushdns.
  3. Locate and delete all folders under: %LOCALAPPDATA%\Microsoft\Office\16.0\Lync
  4. Make sure that you can successfully connect to the Web-Ticket service by navigating to:
    If the URL above connects successfully and a page loads, then the Web Ticket service is running properly and there are no connectivity issues.
  5. Try to delete/renew the user’s SIP certificate.
    1. Open the Certificate Manager by going to Start > Run and typing certmgr.msc
    2. Expand Personal > Certificates
    3. Sort by the Issued By column and look for a certificate issued by Communications Server.
    4. Delete the certificate.
  6. Remove User's URI
    1. Open Regedit and navigate to the following path and delete the folder: HKEY_CURRENT_USER\Software\Microsoft\Shared\UcClient.
    2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office. Then open 15.0 or 16.0 depending on your version of office.
    3. Find the key for Lync and open it.
    4. Delete the Data for the strings named ServerSipUri and ServerUsername.

Try to sign into Skype for Business again. If none of this helps, contact your administrator to open a case with Microsoft.