Hi, I upgraded to El Capitan yesterday and all of the contacts in my Thunderbird Address Book have disappeared. The Address Book is completely empty. Also, it doesn't even have the address books on the left-hand side, e.g. 'Personal Address Book' etc. Are my contacts stored on my machine? If so where are they located and how can I get them back into my address book? I've been adding contacts for a few years. When I compose emails, email addresses are auto-filling in the composition field, so it looks like they are still there somewhere? Thanks.