Recently I'm not getting the option to convert attachments to Box. I have the latest versions of both T-Bird and the Box add-on. I have a valid Box account (and can sign in on a browser), and the T-Bird Add-ons Manager shows Box is activated. Previously (not in recent months) I had no trouble converting files to Box on this computer. I am running Win-10 and have all updates installed, and I have re-started the computer since all updates (including T-Bird and the Box add-on).

What's going on?