Issue Description
Leads and Contacts must have a Last Name and Company Name in order to sync to Salesforce. When this data is not available on records it is recommended to setup a default value for these two required fields by following the instructions listed in the link below:


Issue Resolution
If setting a default value for records is not a workaround for your business goal and you need to sync those records with no information on these fields then you would need to work with your SFDC admin and SFDC's support to modify the rules within SFDC that prevents records from syncing over without a value in the Company and Last Name fields.

Who This Solution Applies To
Customers using Salesforce