External mic works but not on MacBook Air

I have a Samson C01U mic that works perfectly with my early 2015 MacBook Air running Mojave. I just bought a Samson GoMic that worked fine until I tried it with Dragon Dictate. I attempted the DD "calibrate" reading and clearly that wasn't working. From that point on whatever audio program I use the GoMic with – QuickTime, Audacity etc. – distorts the recording so as to make it unintelligible. (It plays back molasses slow, maybe 1/5 regular speed.)

The GoMic continues to work perfectly on my old ChromeBook so the issue is clearly between the GoMic and the MacBook. I fiddled with all of the sound preferences to no avail. I opened the MIDI in utilities and couldn't get it working that way. Googling around I find that the GoMic should work seamlessly with my Air.

I eventually reset the NVRAM and the GoMic started to work again.

Then I stupidly gave Dragon Dictate another go and the GoMic went back to distorted recording. Again, only on my MacBook and not on the ChromeBook.

I tried to rest the NVRAM again but this time it didn't bring the GoMic back to life.

For what it's worth, I have a Samson C01U desktop mic that works fine and always has. Any thoughts?