Key for 3rd currency is not defined for org. unit &1 in ledger &2

What causes this issue?

Sender ledger &V2& conducts values in the 3rd currency. However for
organizational unit &V1& (company code in local tables, company in
global tables) the key of this 3rd currency is not defined in ledger
&V2&.

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?

Procedure for System Administrators

Maintain the key for the 3rd currency in the sender system for
organizational unit &V1& and ledger &V2&.

Error message extract from SAP system. Copyright SAP SE.