[Obsidian Dragon]

Thanks for checking for shared driver usage by user accounts on the system. Is it possible some other application or utility is grabbing the driver? Perhaps QuickTime, GarageBand, MainStage, 3rd-party MP3 Players, Zoom, Spotify, etc.? I'm just reaching for straws now. The fact that audio does go through the interface would indicate the hardware is not the issue. When starting Protools, holding the "N" key usually allows you to choose the audio device for the playback engine again (overriding the default settings). Give that a try, although I suspect you've already done that. Hopefully someone else can chime in with more helpful suggestions. It's Labor Day so many people may be not on the forum--or perhaps many people are free to be on the forum. You never know.