Some Loads for this Reference # have not been selected billing message

When using the combine invoicing feature, the system may occasionally be unable to complete the process. If the message "Ready with Caveats: Some loads for this reference # have not been selected,"  is displayed, it means the charge sets have mismatched net payment terms. In order to successfully combine invoices, the net terms on the charge sets must be exactly the same. 

The net terms information is shown in the Billing tab of a load, specifically in the section that displays the invoice number and invoice date: 

Payment terms can be modified in the Payment Terms section of the customer profile.