Read more at source: http://blogs.technet.com/b/nexthop/archive/2013/11/13/new-lync-online-guided-walkthrough-helps-office-365-admins-troubleshoot-sign-in-issues.aspx
About The Author
Anderson Patricio is a Canadian MVP in Cloud and Datacenter Management, and Office Server and Services, besides of the Microsoft Award he also holds a Solutions Master (MCSM) in Exchange, CISSP and several other certifications. Anderson contributes to the Microsoft Community with articles, tutorials, blog posts, twitter, forums and book reviews. He is a regular contributor here at Techgenix.com, MSExchange.org, ITPROCentral.com and Anderson Patricio.org (Portuguese).