I converted all 25 years of my email to Thunderbird 78 and have an active calendar that I can add to manually but "Events and Tasks" import of an ics file of a new calendar from Outlook does not work. When I try to import, I get the error, MODIFICATION FAILED. I have looked at the eventual calendar items that Thunderbird 78 is trying to import prior to MODIFICATION FAILED and they show likely proper start and stop times but show nothing else just "time busy". I am looking for the calendar event title on the ics file and the detailed body of information stored on the ics file about the event.