The following links provide help for troubleshooting sign-in issues with Microsoft Lync.
- Troubleshooting Azure AD connection configuration errors - Ping Identity support article for troubleshooting Azure AD connection configuration errors.
- Troubleshooting Skype for Business Online sign-in errors for administrators – Describes how to troubleshoot sign-in issues with Microsoft Skype for Business Online. Details how to clear the credential cache that can occur on some operating systems.
- Troubleshoot sign-in issues for Lync for Mac 2011 in Skype for Business Online – Describes how to troubleshoot common issues between Lync for Mac and Office 365.