Object type & and document type & not assigned to content repository &

What causes this issue?

Customizing problem: The specified combination of object type and
document type is not assigned to the content repository.

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

System Response

How to fix this error?

Check the "Links" function in Customizing.
<DS:TRAN.OAC3>Execute Function</>

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.