[Darryl Ramm]

The UI code seeing the Eleven Rack as a USB midi device to control its settings and it being the interface are two separate things. So what is the Pro Tools playback engine set to? Hold flown the 'N' key when starting Pro Tools and select the Eleven Rack. If that is not an option in the menu, you have other problems... The most likely one is that you have not properly optimized optimized your Mac--not disabled sleep as you are supposed to. Or you have manually slept/suspended the system. The system cannot sleep/suspend when the Eleven Rack is connected and powered on. The driver will not recognize the interface when the Mac resumes from sleep/suspend--that unfortunately is Avid driver software working as expected/as badly as designed.

And your Mac mini has a 5,400 rpm internal drive, a combination that can be fairly toxic for Pro Tools and cause all sorts of problems/glitches/artifacts/crashes, you need to work on getting an dedicated audio/session drive. I really recommend SSD drives for performance and reliability reasons, Samsung 840 Evo or Pro SSD drives are great, or if external LaCie make some nice SSD drives, or you are handy or have somebody who can help you you can put a Samsung drive in a third party Thunderbolt enclosure.