Comment 38 for bug 614742

The related branch fixes the missing "Add" button - now the error message appears if login is unsuccessful.

I've prepared an experimental build at ppa:roignac/svn (https://launchpad.net/~roignac/+archive/svn) - please, test this and post here if this helps. Most likely, the error will be "Application request limit reached", so the only way to add Facebook account is just to wait and try again in several minutes.