I have tried moving these rules up and beneath the web access rule but still no luck. The other rule just for the Stun application and any service. One with ms-lync, ms-lync-audio, ms-lync-base, ms-lync-content-sharing, ms-lync-online, ms-lync-online-apps-sharing, ms-lync-video, ms-office365-base, office365-consumer-access, office365-enterprise-access, RTCP, RTP, RTP-base, skype, skype-probe, ssl, stun, unknown-udp, web-browsing, web socket & windows-azure-base applications all with application-default services. Our rules for Skype is split into two rules. The end user just gets a message 'couldnt connect to the presentation' What i can see that when he tries to share his screen according to the logs the action is allowed, his machine goes out to microsoft IP addresses, its not being decryted, its going to ports in the 50000 range (i believe this is the correct ports for S4B) but the application is coming up incomplete, which i think is the issue here. When i check the firewall logs for a particular user nothing is being blocked. Im in a call, but my screen share (or the other persons shared screen). We have had all the rules setup for a long while with no reported issues but today its not working. If you are having issues sharing your screen in Skype, the following tips may. We are getting reports of our Skype for business screen sharing or file sending isnt working today. Screen Sharing Skype For Business For Free Here Is.