Article ID: 2459899 - View products that this article applies to.

Not sure what release of Office 365 you're using? Go to the following Microsoft website:
Am I using Office 365 after the service upgrade?
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When you try to sign in to Microsoft Lync Online, you receive the following message:

To sign in, additional software is required.

When you click Download and install now?, you are prompted to download and install the Microsoft Online Services Sign In Assistant, which can also be obtained by running the Office 365 Desktop Setup Tool.

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Screen shot of Lync sign in page, including error message Download and install now? link


To work around this issue, sign in to the Office 365 portal, and run the Office 365 Deskop Setup Tool to download and install the Microsoft Online Services Sign In Assistant.


This issue occurs if you attempt to sign into Lync Online using Microsoft Lync 2010 on an operating system that doesn't have the Microsoft Online Services Sign In Assistant. 

Still need help? Go to the Office 365 Community website.


Article ID: 2459899 - Last Review: August 29, 2013 - Revision: 22.0
Applies to
  • Microsoft Office 365 for enterprises (pre-upgrade)
  • Microsoft Office 365 for small businesses  (pre-upgrade)
  • Microsoft Office 365 for education  (pre-upgrade)
  • Microsoft Lync Online
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