Resolved! Rogers Webmail: mailbox not syncing - must reauthorize of the Yahoo! app - where in the app?
I have 3 mailbox defined in my Rogers Webmail. One of them, from a 3rd-party server (neither @rogers.com or @yahoo.ca), regularly loses sync: in email settings > mailboxes, it shows as "not syncing" and the message reads "To reauthorize this mailbox,...