Currency type of plan version "&1" is not active in CO-PA

What causes this issue?

You have assigned plan version &V1& to the plan version of your order
or process. The currency type assigned to this version is not active in
operating concern &V2&.

How to fix this error?

Check your settings for the <DS:TRAN.OKEQ>currency type</> used in
version &V1& and the attributes for <DS:TRAN.KEA0>operating concern
&V2&</>.

Error message extract from SAP system. Copyright SAP SE.