JetPack Subscriptions Widget Fails to Display Form

WP: 4.4.1
Theme: Skeptical

I have installed the Jetpack Subscription module in my self-hosting WordPress instance.

I expect to see a functional subscription widget, with input form area for email and an active button. Instead, I only see the text area and an inactive button. My own browser (Chrome) doesn’t give me an error, but my webhost provider (SiteGround) support reports this error message from their browser debugger:

‘An invalid form control with name=’email’ is not focusable.’

(And the invisible input area does indeed have the name ’email’.)

I know through the preview feature that this bug is indeed not present with all themes; that it reproduces if I move the widget; and reproduces on simple post pages. So it indeed seems to be a theme issue, and I suspect (because “email” is a common word) that it’s a namespace collision; but that’s a whole body of work (mainly design based) that I’m not contemplating right now.

Has anyone else has this bug? How did you fix it? If at all…

Skeptical is, BTW, retired.