InfoObject &1 is not a valid hierarchy basic characteristic

What causes this issue?

The InfoObject is not a hierarchy characteristic. In other words, one of
the following points applies:
Hierarchies are not defined as allowed in the InfoObject
The InfoObject is only a reference to another characteristic
The InfoObject is protected and cannot be changed

System Response

Hierarchies cannot be saved for this InfoObject.

How to fix this error?

Use a different characteristic or use the InfoObject maintenance screen
to specify that hierarchies are allowed. In the case of a reference,
create hierarchies for the reference characteristic.

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.