I can’t reactivate the plugin

Are you able to log in at https://wordpress.com ?

yes, I have a valid account there. The problem is your plugin won’t accept it.

Ok, just so we have this clear:

1. You can log in at https://wordpress.com/

2. You are currently logged in at https://wordpress.com/

3. Jetpack will still not accept your WordPress.com account?

correct

I am actually looking at my WP.com account now, and I can confirm that I Jetpack will not accept the email I see in my account on WP.com

Ok, would you please contact us via https://jetpack.com/contact-support/?rel=support so we can take a closer look?

I would, but whatever contact form was on that page has been replaced with:

“We’ve temporarily limited Jetpack support, but remain fully open for our paid Jetpack plan customers. …”

Ah sorry, you’re right. Please send an email to support (at) jetpack (dot) com

I sent the email, and I have not gotten a response.

Sorry for the delay. We’re working through a backlog on the support queue at the moment, but I’ve confirmed we have received your email, and someone will reply as soon as it reaches the top of the queue.

Please don’t send additional follow-ups on that ticket, as each new reply causes it to go back to the bottom of the support queue, meaning it takes longer for someone to get to it.