Hardware Volume Control for the Chord Mojo

I have a Chord Mojo working correctly with the latest version of Volumio on a Raspberry Pi 3 model B. Under “Playback Options” > “Volume Options” I have the mixer set to “Hardware” and the mixer control name as “Mojo Validity.”

However, I cannot control the DAC’s volume with Volumio.

Has anyone else experienced this? I’d like to avoid using the “Software” mixer.