Thunderbird 91.4.0

I have IMAP enabled, and have been using Zoho mail account in Thunderbird for years with excellent results.  Thank you Zoho.  However starting yesterday (12/10/21) I cannot tag messages in my Zoho mail accounts.  I am using imap.zoho.com as my server.  I have tried all the Thunderbird troubleshooting, disabling addons, upgrading from a 7x version (from the Debian repos) to the latest, checking file and dir permissions and cannot solve.  My other IMAP accounts work fine.  Any ideas?  I use several free emails and several paid accounts, all are affected.