Direct access is not supported for hierarchy DataSource &1

What causes this issue?

The hierarchy DataSource &v1& supports data transfers via IDocs only.
Direct access to hierarchies of this DataSource is not possible for
technical reasons.

System Response

The request was rejected.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.