Contract object types not defined for specified revenue types

What causes this issue?

The objects to be processed have contract object types that were
assigned to a different revenue type to the ones being billed at the
moment.

System Response

The program could not create any billing documents.

How to fix this error?

Assign the contract object types to the specified revenue types, or
select a different revenue type in Customizing for <ZK>Contract Accounts
Receivable and Payable</>.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.