Do I still need to have a College Board Professional account if I am downloading AP score reports via the web service?

Yes, a College Board Professional account is still required to authenticate and authorize your access to the web service, and to track your most recent downloads. You must also make sure that you log in to the new portal at least once with your account to accept the site terms of use before starting to use the web API, otherwise it will fail. Learn more by visiting Downloading Using a Web Service.