I received this by email not long ago.
Can you try adding the API key below, when I do it I get the error message. I’ve never had this problem before and I am hoping you as owner may have workaround? API Hidden
First up, this is a Mailchimp error, not Ourlocality, as the roles are not related to WordPress. It should not make any difference who owns the website, as even the superadmin got the same error with the same API.
A different API worked fine, so there is something wrong with the API.
This is a Mailchimp plugin, so they should be able to provide support to paying users for errors generated at their end.
Check this post on how to raise a ticket, if you pay for a mailchimp account:
and the general instructions: