For the past two days when start Thunderbird and synch Cardbook with my Google Account I receive a message that I need to sign in to my Google Account. I do so and get a message that “This app is blocked”. However, when I log onto my Google Account and look at Security: 3rd party apps, Cardbook is authorized. What is going on? This happens on both my and my wife’s (almost) identical computers. I have not updated TB, CardBook or Windows on either computer in the past few days. Windows 10 is up-to-date.