I recently ran the offered system update for my Ubuntu 18.04 installation. Everything appeared to go well even if it did take over an hour and I was quite happy whit how it all turned out. However I've just noticed that the calendar that I was running in Thunderbird 60.20.1 has disappeared. This is a real pain as I use the calendar a lot and have a lot of reminders set in it.
Can anyone advise; Has the calendar just been de-activated and can be re-activated? If so how do I do it? Or Have I lost everything and have to start again?