After upgrading from Lync Server 2013 to SfB Server 2015 we tried copying and pasting images into IM windows and got the message that File Transfer is turned off.
I logged into the Lync FrontEnd server to run the command Get-CsFileTransferFilterConfiguration and the action was set to block.
Next I started up the SfB Control Panel to look at the Global Policy for FileSharing under IM and Presence, and what I see is that nothing is blocking PNG files, or JPG files, so why can’t I send files? I also tried allowing peer to peer file transfers under Conferencing, but that didn’t help either.
I ran wireshark on my PC when i was pasting the file/image into the typing area, weirdly enough I didn’t see any traffic going to Lync FE or Edge server, which tells me its a policy in the client that I need to update somewhere, since it isn’t even making it out of my computer. I tested again, but send a regular text message over Skype and saw the packets go to the FE server.
Resolution: I ended up going to the Conferencing tab and modifying the Global and Desktop and Application Sharing policy to Enable peer-to-peer file transfer and then waiting for it to update and had to restart the Skype client on my PC and the users I was testing with before it started working.