Salesforce - Mailchimp integration - "requested resource could not be found"

Salesforce - Mailchimp integration - "requested resource could not be found"

I am importing from Salesforce and connecting to Mailchimp.  All the fields that were mapped showed up correctly in the log. 

However, the import was unsuccessful because of the following error:

"The requested resource could not be found."

What is the requested resource referring to?  Something in Salesforce or Mailchimp?