Invoices can be found in the new partner portal. This article will describe how to access your own invoices but also the specifications from your customers.
Make sure you have a login on the general Partner Portal Profile.
Login to the partner portal: https://copaco.cloud/partner/
Go to Invoices.
Click My invoices to see Invoice from Copaco to you as a partner.
Click Customer specification to see a specification of subscriptions from a specific customer.