Why does field mappings from Salesforce to Mailchimp not work?
Field mappings are trigger based so when you edit a record that is on a Mailchimp audience which has filed mapping set up we will attempt to update the corresponding record in Mailchimp. This can fail for several reasons. If that does happen try the following -
First, check whether other updates (such as name changes or other field edits) are successfully pushing to the Mailchimp member. If only one field is failing, it may be a field mapping issue
Try the Refresh on the Mailchimp for Salesforce Contact page component, it runs a Mailchimp → Salesforce (MC>SF) refresh. If this refresh shows a failed badge, it can indicate there’s an issue with the record that may also prevent updates from syncing in the other direction.
If the related Mailchimp member is marked as cleaned or unsubscribed, Salesforce cannot push updates to that record. Only subscribed members can be updated.