Did you receive an email that looks something like this?
This likely occurs when the synced MailChimp lists are manually removed from your MailChimp account. If you or no one made manual changes to your MailChimp account, this is may have been caused by something else that shows a mismatch in your sync settings and your account.
To prevent any issues (e.g. overbilling), we require you to confirm and resave your synced settings.