Good idea, thanks. The output is huge, too long to be useful. So I used
diff between my original and this one and it looks like it misses the pattern for "Inbox" even though both mbsync and mutt print that directory as "Inbox". So I tried all upper case and that worked.
Here's the part of the diff from my original that shows it syncing my INBOX. I have truncated that last line due to the length and because PII...
< M: Enter select_box, name=INBOX
< M: Leave select_box, ret=0
< S: Enter select_box, name=INBOX
< S: Leave select_box, ret=0
< S: Called get_box_path, ...