New Plantronics Blackwire C3210 headset gets "Error opening sound device" message

I'm doing Azure Online Training & have read through many instances of sound device errors in this forum and am still stumped. I am using Audacity 2.3.3 on a MacBookAir mid-2012 with Latest MAC OS. I have a new Plantronics Blackwire C3210 headset (mono/one earpiece) that outputs audio on Garageband, iTunes, and web videos (through YouTube, Amazon Prime) but I get an "Error opening sound device" message when I try to play a recording made by or imported into Audacity 2.3.2. My other headset (Logitech USB Headset with two earpieces) works but I'm not a fan of the two earpieces. (It is brand new and works well, but I have always preferred a mono headset since I can only hear out of my right ear.) Note that I am selecting the correct USB headset on the Audacity settings, and I've checked my Audacity preferences and the Audio MIDI setup app. All seems to be set properly. I suspect the headset is defective but can't be sure until I've ruled out any Audacity settings that I am missing.