The Lync web app is a browser-based alternative for joining Lync online meetings. For it to work, the browser must have Silverlight enabled. Silverlight is a cross-browser (Internet Explorer, Safari, Chrome, and so on.), cross-platform (Mac, Windows, and Linux) plug-in that enhances user experience and the delivery of applications on the Internet.

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Mar 01, 2017 Now try installing the Lync Web App Plugin again, which should now work just fine. OPTIONAL: In Firefox press CTRL+SHIFT+A to open Add-Ons, go to Plugins and set 'Microsoft Lync Web App Plug-in' to 'always activate', so that your user saves some clicks. User friendly. OPTIONAL (or 100% needed for some admins): Revoke the admin rights for the user. May 10, 2017 Microsoft Lync is the new rich client for Lync users on the Mac platform and offers integrated functionality for instant messaging, presence, conferencing and voice. Lync for Mac is designed to work with both Lync Server 2010 and Lync Online to help you. Microsoft Lync for MAC – This app was created by Microsoft Corporation and updated into the new version at March, 15th 2017. Download Microsoft Lync 14.4.3 for Mac from Apps4MAC.com. 100% Safe and Secure A powerful Mac software that provides its users with real-time collaboration. Lync Web App allows for the sharing of a desktop, an application (not on a Mac), a whiteboard (not on a Mac) and a poll (not on a Mac). Note: Lync Web App Plug‐in is not supported on 64‐bit browsers, or on 32‐bit Safari browsers except for Macintosh OS 10.4.8 or later (Intel‐based).

Attending a meeting by using the web app is similar to attending the meeting by using the desktop client. The advantage of using the web app, however, is that the participants do not need to install additional software to attend and view online meeting presentations.

When using the web app, you will not be able to use the Present a PowerPoint feature of Lync. In addition, voice and video capability is not yet available for the web app, so participants must connect to the audio portion of the meeting by using a dial-in number.

To join a Lync online meeting by using the web app:

Open the Online Meeting invitation.
Click the Join online meeting link or copy and paste the meeting URL into a browser.
Complete the onscreen information, such as your e-mail address, and click Join Meeting.
Enter your office or cellphone number on Phone Details and click Call Me.
The Online Meeting calls you and connects you to the conference.

Install Lync Web App Plug-in

I had some strange problems with Skype and Office 2016, too.

The solution was easy: Office 2016 (Professional Plus in my case) installed its own Skype for Business software, which block the execution of the 'SkypeForBusinessPlugin.msi'

When you open 'Apps & Features' and choose 'Modify' , you should see 'Skype for Business' in the list.

Once you removed that feature, you should be able to run the web plugin, that usually is deployed, when you open a meeting.

Maybe that link helps with getting the right installer:
Trouble installing the Skype for Business Web App plug-in?

Microsoft Lync Free Download

Hope it helps ...

Download Lync Web App For Mac