Consider the following scenario:
Google Chrome is configured as your default browser.
Your Google Chrome installation has been upgraded to version 42 or a later version.
You try to join a meeting by clicking a "Join Lync Meeting" or "Join Skype Meeting" link, and one of the following conditions is true:
You click the link within any application other than Microsoft Outlook 2013.
The meeting organizer did not create the meeting by using the Outlook Lync or Skype for Business meeting plugin.
The meeting organizer is from another organization that has not configured the option to preserve the Transport Neutral Encapsulation Format (TNEF) for outgoing email messages. For more information, see the following Outlook website:
When you click the "Join Lync Meeting" or "Join Skype Meeting" link in this scenaro, the locally installed Lync or Skype for Business client doesn't start. Instead, the default web browser starts, and you are directed to the Lync Web App or Skype for Business Web App webpage. Then, you are prompted to install a plugin, or you are joined to the meeting by using the web experience.
This problem occurs because, by default, the updated version of Google Chrome deprecates and disables support for the Netscape Plugin API (NPAPI). NPAPI is currently used as part of the client detection process for the Lync or Skype for Business client when you join a meeting by clicking a link. When NPAPI is disabled, the webpage cannot determine whether you have the client installed.
To fix this issue, install the April 2016 Cumulative Update 4.0.7577.728 for Lync Server 2010, Web Components Server.