Entity type & is not assigned to any object type in Object Repository

What causes this issue?

You want to change from an entity type to the assigned object type.
This is not possible because the entity type has not yet been assigned
to any object type.

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?

The entity type is assigned to an object type indirectly via a data
model of the type business object.
First check whether the entity type is assigned to a data model of the
type business object. If not, you can create an assignment in the
Data Modeler.
Next, check whether the data model is assigned to an object type. You
can maintain such an assignment in the Business Object Repository in
the basic data of the object type.
If you want to create a new object type for the data model, you can
switch directly in change mode from the data model to creating the
object type. The short description of the data model is transferred
automatically.

Error message extract from SAP system. Copyright SAP SE.