"Cannot connect to server, Retrying............."
I encountered this message myself on several occasions during a Lync call using my mobile device. The Lync 2013 mobile version will establish connection to the Lync Reverse Proxy (It can be Microsoft TMG 2010 or IIS ARR). In my case I am using the IIS ARR which is highly recommended now by Microsoft (Actually Microsoft is pushing for this method) since Microsoft discontinued any future release for TMG 2010.
To solve this issue, i increased the Time-out setting in the IIS Server Farm Proxy as follows:
- Open IIS on the Reverse Proxy server and Navigate to the Server Farm.
- Open the Proxy and increase the time-out settings (Default is 200)
This should be done to both the Lync Discover and External Web Services URL/Farm.
For more information about the recommended/Qualified Infrastructure for Lync 2013, check the following URL http://technet.microsoft.com/en-us/lync/gg131938
