I just wanted to add that many weeks ago when I started building this site and when I installed Jetpack I did a test subscribe in my own email, and got a confirmation from Jetpack that I was a subscriber. So this worked at one time. But this evening when I tried to do another test subscribe (using a different email address) on the front end it said something like there was an error in processing. I don't remember what it actually said. But then I checked the widget backend and found this error message.
Now I can't even get the widget to appear in the front end to test it. In the backend the error is now reading: -10520: Jetpack: [http_request_failed] couldn't connect to host