"Could not reconnect to Audio/Midi Device" with Focusrite Scarlett 18i20

Hi Community,

I just purchased a Focusrite Scarlett 18i20 (USB 2.0) interface and I am having a little trouble getting it started.
Whenever I try to create a new project it gives me the error “Could not reconnect to MIDI/Audio device”. The problem does not exist if I select the internal soundcard or if I hook up my old interface and use that.
What am I overlooking? I am using low latency kernel version 4.2.0 on Ubuntu Studio 15.10, with Ardour 4. From posts I read here before buying, the entire Scarlett line has been supported since kernel 3.19, no?

P.S. I can provide whatever other details necessary to diagnose this problem. My username is part of the “audio” group.

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