I am trying to access Describe Opportunity REST API. I am getting error "Opportunity API disabled". I read the docs and it says "The Opportunity API is not supported for CRM-enabled subscriptions". Is it the reason to get "Opportunity API disabled" error?
The opportunity api is meant to be used by those companies that don't already have a CRM integrated with their Marketo instance. If you're already integrated with SFDC then you'll need to access the opportunity information from there.