My husband checked, and that doesn’t seem to be the problem.
Sometimes when we’ve run updates, the next day a correction comes down; we’re kind of waiting to see if that happens again...
(The one thing we haven’t tried is sticking ear plugs directly into the speakers; I’ll try that and get back.)
If you have a spare set of speakers, try using those to see if it works. The sound card and software seem to work since they are working through your ear phones.