Consider the following scenario:
You configure the Region and Language format to Turkish (Turkey) for your computer in a Microsoft Lync Server 2010 environment.
You try to join an online meeting by using Lync Web App on the computer.
You select the Join as a guest option and then input a username in the Lync Web App window.
You click the Join Meeting button.
In this scenario, the following message is displayed in the window continually. However, Lync Web App does not join the meeting.
Joining the meeting...
This issue occurs because Lync Web App does not fall back to an English version when you try to join the meeting.
To resolve this issue, install the following cumulative update:
2953588 Description of the cumulative update for Lync Server 2010, Web Components Server: April 2014