The reference and target cost center group must be identical

What causes this issue?

You want to copy an object group and have specified a different object
group as the target entry.

System Response

Since the reference objects are not assigned to the target objects, you
cannot copy with this combination.

How to fix this error?

Correct your entries. The following is a list of the possible
combinations for copying the planning:
all objects -> according to reference
one objects -> according to reference
one object -> different object
one object -> object group
object group -> according to reference

Error message extract from SAP system. Copyright SAP SE.