Zoom H4N support in Reaper

Reaper won't record my H4N 

I'm new to both the H4N and Reaper. I've connected the H4N to my Mac via USB, and I do see that the input is recognized in the Mac OS, but I can't get a signal from the H4N to a track. - In Reaper Preferences/Audio/Device "H4" appears as an option, and I have selected it - I have armed a new track for recording - When I test the mic, no signal is recognized. What am I doing/not doing? Thanks in advance for any help!