API key no longer working

I’ve been using AutoChimp with no issues thus far, but as of a couple days ago, it stopped working. My mailing lists are no longer showing up and it doesn’t seem to like my API key anymore.

Unable to retrieve your lists with this key! Did you paste it in correctly? Visit the API Key tab and try again, just in case. If you know it is correct, make sure you’re connected to the internet and not working offline.

Nothing has changed, so I can’t understand what happened. I’ve tried creating a new API key and pasting it, but same issue.

Any help?

http://wordpress.org/plugins/autochimp/