Company code & already assigned to CO area &

What causes this issue?

You cannot create a second controlling area with company code &V1&
assigned to it because company code &V1& is already assigned to
controlling area &V2&.
Note: <GL:assignment_control>assignment control</>.

How to fix this error?

If you still want to create controlling area &V1&, change the
assignment of company code &V1& to controlling area &V2& (provided this
is still possible for consistency reasons) to ensure that company code
&V1& is not assigned to a controlling area.

Error message extract from SAP system. Copyright SAP SE.