Your site doesn’t seem to be properly connected to WordPress.com at the moment. Could you try the following:
1) Go the Jetpack menu in your dashboard
2) Click on “My Jetpack” at the top of the page.
3) Click on “Disconnect Site from WordPress.com” if your site is currently connected to WordPress.com.
4) Confirm the disconnection.
5) Click on the Connect button to connect your site to WordPress.com again.
Once you’ve done that, go to Jetpack > Settings and make sure the Subscriptions module is activated.
You’ll also want to go to Appearance > Widgets, and drag the Blog Subscriptions widget back to where it was.
Let me know how it goes.
Thanks very much. I had disconnected and reconnected yesterday, no luck, but now I’ve turned the Subscriptions module back on. I’m not sure how it (and the Social module) got turned off, but all seems well now.