Really Microsoft? Something went wrong. I suppose it would be way too much trouble to say WHAT went wrong, or give any other diagnostic information at all. Talk about inane!
So I went to the Service status link, and it shows OneDrive up and running. OK, but not in MY case. So I try another login I have and it works fine. Apparently only the documents and files I have under THIS account are (I hope temporarily) unavailable. Good job I didn’t have business critical data in there.