We use Office Web Apps server to use browser-based versions of Office apps such as Word, Excel, PowerPoint in our on-premises environments. Some features of Exchange Server, SharePoint Server and Lync Server relies on Office Web Apps server to work properly.
I had been trying to use PowerPoint sharing feature in Lync 2013. I got the following error. Then I installed and configured Office Web Apps server and the error has gone!
Sorry, we couldn’t upload abc.pptx because we’re having trouble connecting to the service. If this keeps happening, try contacting your support team.

Solution: Installing Office Web Apps server
Here are some useful links which can help you with installing Office Web Apps server:
- Installing Office Web Apps and configuring Lync Server 2013:
http://howdouc.blogspot.com/2012/08/installing-office-web-apps-server-for.html - Creating and configuring certificate:
http://msmvps.com/blogs/andersonpatricio/archive/2012/11/20/office-web-apps-server-configuring-certificates.aspx - More details from Technet:
http://technet.microsoft.com/en-us/library/jj219455.aspx