I have a local carddav server (via Baikal) and was testing various CardBook modes against it. I noticed that when I add a new addressbook and uncheck the ‘Offline’ checkbox, newly created contacts do not sync to the server, and contacts on the server do not show up. When I manually run Synchronize, the console log says “Synchronization not tried”. In Wireshark, I see no network activity whatsoever when creating new contacts or pressing Synchronize. If I uncheck/disable the address book, all the local contacts I entered so far (shown in bold) are permanently lost.
I can’t tell if it’s a server configuration issue, or if I’m running into some edge case, or if the mode is completely unsupported. I tried it with latest thunderbird and cardbook version from AMO, and it still happens.