I am now getting this popup even though I am not trying to connect to Gmail

Hello, I use Thunderbird to retrieve my AOL mail. Starting today, when I start Thunderbird it retrieves the AOL mail and then after a couple minutes I get the attached popup. I am not trying to connect Thunderbird to any Google account and I don't understand why I would get a message saying to use Google to sing in to Thunderbird. Once this popup occurs Thunderbird will not connect to AOL until I close it and restart it. I do have GMail set to forward messages my AOL address but this screen has not come up before Any thoughts? Thanks, John