The Microsoft Support team just released a comprehensive article that describes how to troubleshoot sign-in issues that may occur when you use Microsoft Lync 2010 together with Microsoft Lync Online in a Microsoft Office 365 environment. Read the article at How to Troubleshoot Sign-In Issues in Lync Online.
Author: NextHop
Publication date: August 24, 2012
Product versions: Microsoft Office 365 for enterprises, Microsoft Office 365 for small businesses, Microsoft Office 365 for education
Topics include:
- Scoping the sign-in problem
- Lync Online sign-in error messages
- Resolve Lync 2010 client-side issues
- Resolve Lync cached endpoints
- Resolve certificate-related errors in Lync 2010
- Resolve DNS and network-related sign-in problems
- Bypass Lync 2010 Autodiscover and DNS resolution
- Resolve user identity and Office 365 authentication system issues in Lync 2010
- Next steps, if the issue is not resolved
- Diagnose authentication issues by using MOSDAL and Snooper
Lync Server Resources
- Lync Server 2010 Documentation Library
- DrRez blog
- NextHop blog
- Lync Server and Communications Server resources
I went through weeks of this following the support materials available up to that point. I finally reinstalled everything. That was the only real fix.
Also Firewall. I've seen problems when firewall was not configured correctly.