You have changed the leading ledger from &1 to &2

What causes this issue?

You have changed the leading ledger. All company codes have to be
assigned to the leading ledger.

System Response

The system checks that all company codes are assigned to the leading
ledger. If this is not the case, these entries will be created
automatically when you restart the ledger customizing transaction.

How to fix this error?

Save your work, exit the transaction, and restart the transaction. If
the change is possible, the system will add any missing company codes to
the leading ledger.

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.