Rated 4 out of 5 stars

After the latest update which happened automatically this addon has stopped working.
It removed my address book and the shared does not even sync.
I run on Thunderbird 52.xxx and the addon should work up to 55.xxx, but as said. The menus are greyed out.
Until Yesterday it worked all fine, but today it is full stop. I cannot use my 900 addresses on the CarDAV server.
All menus are greyed out and cannot be accessed. When I try to add the old address book no new address books can be added. The shared address book is not sycnhronising either.
I have this on a different computer and it works fine on the same version of Thunderbird.
I use the OpenSync on the Android and there it works fine too.
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All is solved, I had a corrupt local DB for the CarDAV/Cardbook and I reinstalled Thunderbird and the addons.
All is working fine now with no problems.

The addon Cardbook is very good and I do agree on that Thunderbird should use this as their standard Address book.

This review is for a previous version of the add-on (21.7). 

CardBook works with Th. 55... may you contact me by email (you surely have indexedDB errors in your console....)

may you try the very last version (21.8) ?