Whilst data is arriving in Engaging Networks Import Records, some fields such as EN_Connector_last_name__c are not being populated.
The reason some data fields may not be being populated is due to the header name in the CSV file.
When the Engaging Networks Import Record object was originally built, the fields added were created with an 'assumed' naming convention.
For example :
A field is created in Engaging Networks and is named 'First Name'. On coming into SF, the tool lower cases the header and replaces spaces with underscores. Therefor, it matches with EN_Connector_last_name__c.
Another field is created in Engaging Networks and is named 'Email'. As the default field on the Engaging Networks Import Records is EN_Connector_email_address__c, it will not match.
Solution : In Engaging Networks, due to being able to flexibly name fields under the Default Supporter Record, it is required to make sure the fields 'map'. Use the Custom settings: Engaging Networks Import Field Mapping to allow the tool to know how to 'map' this data coming in.