This error occurs when a required field in your Marketing Automation does not have value or it is blank when syncing to your CRM.
|11 Apr 2019 11:39:29||INFO||Updating from Mailchimp to Salesforce|
|11 Apr 2019 11:40:02||ERROR||Unable to sync record because Last Name is blank.
Contact [id=c99400695a0befe288c4b3859b554c2d, emailAddressfirstname.lastname@example.org, firstName=, lastName=, created=2018-06-14T19:50:20.000Z, lastUpdate=2018-09-19T16:41:41.000Z, ]
For Salesforce subscribers see Step 1 of your integration to enable this feature to use "Unknown" if First or Last name is blank.
You will need to have these required fields filled up in your Marketing Automation software or reach out to our 24/7 Support Team to enable the CRM customization for the error containing, First name or Last name is blank.
If the error is just Required_Field_Missing then the solution could be to set these fields as "not required" so that the error will disappear.