Customer objects can only be created as test objects at SAP

What causes this issue?

This SAP System is designated as an internal SAP system. The object
&V1& &V2& therefore cannot be edited in the customer package &V3&.

System Response

Editing is terminated.

How to fix this error?

Assign the object &V1& &V2& to a package that does not begin with Y or
Z. Objects from a name range reserved for customers can only have local
packages or test packages (1st character = $ or T) in internal SAP
systems.

Error message extract from SAP system. Copyright SAP SE.