What causes this issue?

For this requirement, incoming documents are not defined in Customizing.

System Response

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

How to fix this error?

Contact your system administrator.

Procedure for System Administrators

Define incoming documents for the specific requirement in the
Customizing activity <ZK>Product Compliance -> General Configuration ->
Regulations and Compliance Requirements -> </><ZH><ZK>Specify Checks for
Compliance Requirement and Check Criteria</></>.

Error message extract from SAP system. Copyright SAP SE.