Hi thailamng-9584,
Does this issue persist all the time? Or what do you do before this issue happened?
According to the error message, it recommends you check if the ports 443, 3478 and 50000 are opened on firewall. For more details about how to troubleshoot the network issue for presentation, please read this article: https://social.technet.microsoft.com/wiki/contents/articles/36407.skype-for-business-troubleshooting-we-couldnt-connect-to-the-presentation-because-of-network-issues.aspx.
Meanwhile, go to the shared file, in general on SQL server, open 1-WebServices-17\ StorageService folder, to check if the PowerPoint file is here.
In addition, do an office repair to see if it can fix it.
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