When attempting to view or share a Powerpoint presentation on Lync 2010, the users got the following message:
This slide couldn’t be downloaded. Please contact your support team. Error reason: File not found.The fact that 2013 clients were unaffected by the Powerpoint presentation is not unusual. Lync 2013 offloads Powerpoint content rendering to the Office Web App server. Lync 2010 clients are unable to utilize this feature, and fall back to the original method, which is managed and rendered from within the Lync server itself.
Of course, my first step in troubleshooting is to plug the error message into my favourite search engine. It came up with several different options, mostly dealing with issues with Office Web Apps, which we weren't experiencing. One blog post in particular caught my attention, because it talked about the same issue happening after a file share move: http://paulbrown.us/blog/2011/11/02/how-to-change-lync-server-file-store-location/. Incidentally, it appears that the writer (Paul Brown) enjoys sitting on active train tracks in his spare time, which may account for his lack of activity since May 2013.
So, Paul Brown (RIP) managed to solve the issue for Lync 2010, which definitely helped me solve it for 2013. The key difference between 2010 and 2013 in this case is that the MeetingContent and MeetingFiles virtual directories in Lync 2010 don't exist in 2013. All that seems to have been rolled into the CollabContent virtual directory in Lync 2013.
When I looked at the advanced settings for the CollabContent virtual directory, the Physical Path still pointed to the old file share location. I updated the location using the new path in both the Lync Server External Web Site and Lync Server Internal Web Site and repeated this on each server in the affected front-end pool, followed by an IISReset. This was enough for both file sharing and presentation sharing to function properly for Lync 2010 and 2013 clients.
This is obviously a bug within the Topology Builder/Lync Deployment Wizard, because this should have been changed automatically by running the Deployment Wizard after the topology change to move the file share.
As a final note, if you're planning on sitting on train tracks, make sure to keep an eye out for any oncoming trains, because, well you know, YOU'RE SITTING ON TRAIN TRACKS!