Setting up my IMAP account on a new Thunderbird installation, some but not all of my folders appear. The missing folders are about five annual archives of Read or Sent messages, for example 2005 and 2006 appear in the list, then no folders for 2007 to 2012, and folders for the years 2013 to 2020. All the folders are checked in the list of subscriptions for the account (right click account name in lefthand list, choose 'subscribe...'). '''Solution:''' uncheck one of the invisible folders, close subscription list. All the other missing years folders appear. The resubscribe to the one unchecked folder and that too is visible now.