You must unrate those usage inputs that are already invoiced. That means you created credit and rebill type of credit memos without selecting the Unrate the usage inputs checkbox. For more information, see Credit and Rebill.
Conga Billing enables the Unrate the usage inputs checkbox only:
- If the invoice, for which the credit memo is created, has at least one invoice line item that has a usage schedule
- After you select the select Auto Apply Credit To Invoice checkbox