Thanks for the suggestions, James. Alas, neither of them is helpful:
1) The Mooshimeter pairing doesn’t appear in ‘settings->bluetooth’. I actually tried wiping out all the pairings that DO show, to no avail.
2) The Android device I connected to in my troubleshooting efforts is now in a different state. As in state of the Union. It’s two thousand miles distant. If it’s the culprit, kudos on the Mooshimeter’s range!
Additional information: I can also connect successfully using an iPad running iOS version 10.2. Unfortunately, the one compatible device I actually own still won’t connect.