I have an external user who cannot open an .mpp file from our PWA project center. She gets a familiar some files contain viruses warning, but when she clicks Yes that she wants to open, nothing happens. I sent her the file in an email as a test and she can open it fine. She does have the PWA domain in her IE Trusted Sites list. I would be grateful for any troubleshooting ideas. We are using the latest build of Project 2016.