Hi, I am a beginner TB user. I upgraded my Thunderbird to v78.1.1 and all of my calendars switched off. I have tried adding the calendars again but I get this error: An error occurred when writing to the calendar Gmail! Please see below for more information. DETAILS: Modifications failed. If you're seeing this message after snoozing or dismissing a reminder and this is for a calendar you do not want to add or edit events for, you can mark this calendar as read-only to avoid such experience in future. To do so, get to the calendar properties by right-clicking on this calendar in the list in the calendar or task view. The calendar that becomes visible/enabled is just 'Read only'. I can't add events to it. I have already tried enabling and disabling Provider for Google Calendar and restarting TB. I have already tried using Public address 'iCal format' and 'Secret address'. In TB, I choose iCS and CalDAV both when trying to get it working. I can't find the guide I used to setup my calendars originally. I do not know which was the right option. There was no pop-up requiring me to enter my Gmail account details. (I am testing with setting up an account for which I do not sync emails) How can I deal with this? Thank you for your time. Sajid.