Curr. type &1 of ledger &2,comp.code &3 is not defined in leading ledger

What causes this issue?

You company code &v3& in ledger &v1& contains currency type &v2&, which
does not exist in the leading ledger.

System Response

In the universal journal entry, there is currently a restraint that
non-leading ledgers may only contain the currency types found in the
leading ledger.
This restraint existed previously as well, meaning this ledger is
currently inconsistent.

How to fix this error?

This currency type will not be migrated. That is, the ledger will not
contain this currency type. Determine if this ledger is still in use and
if it should be migrated without this inconsistent currency type.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.