If the marketing effort is created from a communication template with the option 'Override appeal business units in the effort and/or in segments' the business units from the appeal will not be applied to payments entered using the source code. This option allows you to select a business unit on the marketing effort directly.
To apply the business unit from the appeal ensure the communication template used to create the marketing effort does not have the option 'Override appeal business units in the effort and/or in segments' marked.