The third currency cannot be activated

What causes this issue?

You have tried to activate the third currency of ledger &V1&. You
cannot do so because a third currency has not yet been defined for
ledger &V1&.

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?

If you want to activate the third currency of the ledger, you must first
define the third currency in the ledger master data.

Error message extract from SAP system. Copyright SAP SE.