Thunderbird installed an update on 21st June. Since then, my email is working fine, and my Calendar tab is present, but there are no calendar entries at all (it's like a new empty calendar). I had a look at the help topics, but I can't find an option for my situation. I've followed the guidance in http://kb.mozillazine.org/Recovering_a_profile_that_suddenly_disappeared which says to first determine if it is a lost or corrupt profile. My address book is populated, and my email is working fine, which suggests it is not a lost profile. So I moved onto checking if the profile is corrupted, but the pref.js file contains the mail.account strings, and the guidelines don't give an option for this (i.e. there's an A or B choice in the help guidance, but my problem doesn't fit into either). I'm not sure this is important, but after the calendar disappeared, a couple of calendar reminders that I had previously ignored (i.e. not snoozed, but just closed the window) popped up, and continued to do so if I just closed the window, but once I snoozed them, they never reappeared (and I can't see the entry in the calendar). My Calendar Data folder has a loacl.sqlite file (736kb). I'm a bit stuck now. I'm running Windows 10.