OK, no help needed. After driving it a few times over a few days, the "AWD Disabled" message cleared itself. LOL.

I was quite happy having successfully replaced the alternator on my XC70 and seeing the battery voltage jump up past 14V, but then I realized I had the AWD Disabled message on the dash. I've never seen this before, so it seems unlikely to be a coincidence and I must have done something to cause it. ...