I'm getting the "Failed to open device" message too. The problem persists after reboot, changing cable, and changing USB port. I able to read midi messages sent by the BeatStep hardware on the same computer with Max6, so the basic hardware is working.
The MIDI Control Center software shows the BeatStep connected, but does not synch with it, update it, or reprogram it.
Computer is a mid-2012 MacbookPro with OS X 10.9.2, Intel Core i7, 8GB ram.