Access Token for Configuration API?

I’m working on an application that has used Access Tokens from Oauth to make calls to the customFields API. We are moving over to the configuration API and I keep getting App Does not have access to this endpoint. It does work with API key but would cause major changes to our app so I know I have the configuration API setup correctly but wonder why AccessToken isn’t supported.

Is there more I need to do to make sure my app supports this? Will it work in the future?
Thanks