The Data Source is set to another source that is not usable for Email Messages and Email Templates. To verify the Data Source of a list:
  • In NetCommunity, navigate to Email > Lists
  • Find the list name and click the pencil on the left to Edit
  • Under List Properties tab, click on Properties below
  • Note the Data Source field
  • If it's other than Imported List, perform the import again. Be sure to select Imported Lists as the Data Source for the list.