The update possibly didn’t connect to the audio driver. Go to the user forums for the type Linux and post a question on how to recover/install/reinstall that driver.
Well, I tried plugging plain old ear plugs into the speakers, and that doesn’t work either. So, it could be a problem with the speaker connections even though it doesn’t seem so.
(We don’t have Bluetooth speakers; ours are plugged directly into the sound card.)
We’ll try your suggestion, Fai Mao.
This isn’t crucial - my cheap little Bluetooth ear buds still work. Thanks for everyone’s suggestions - this is husband’s busy time at work, but we’ll be able to solve it after tomorrow. We’ve just never experienced it before; for over ten years, Linux has been great for us, without a single problem.