When e-commerce data is synchronized and customer data is transferred to Mailchimp, depending on the synchronization mode, either an existing subscriber is enriched with e-commerce-relevant data or a new subscriber is created with the status “subscribed” or “transactional.” If the person's first or last name is missing, this is because the merge fields for first name and last name no longer correspond to the standard specified by Mailchimp.

The merge field for first name should be called FNAME and for last name LNAME