The routine steps of restarting the computer, unpairing and pairing the headset, and glaring angrily at every bit of electronics in the room, had yielded no improvement, so there we were.
Then, on the first live video call using the headset, the other side’s speech was totally garbled. Pairing with the Windows 10 laptop was easy, and the headset worked fine for one brief test call via Microsoft Teams, I was told. The headset had worked perfectly when paired to a phone to test it.