Print Receivables Transactions completes with error

Summary:

When attempting to run the "Print Receivables Transactions" process for a single invoice, we are getting below error:

The bill-to customer email address for transaction couldn't be determined. This transaction won't be included in the output.

The email configuration for the business unit is incomplete. Transactions belonging to this business unit aren't included in the output file.

Business error returned in email delivery setup

We have already checked the following :

The customer Contact has been created with Role type : Contact

Generate Bill Flag should be set to YES at the Transaction

Preferred Deliver Method is set to ‘Email’

I am not sure what else is missing.Please help