Schedule C is NOT a business client. That might be part of the confusion. Business client files a return other than a 1040. 

Contact Support EITHER https://proconnect.intuit.com/community/proconnect-tax-news-updates/discussion/proconnect-tax-assist... OR https://proconnect.intuit.com/support/en-us/help-article/intuit-account-settings/contact-proconnect-...

ALSO Any client can be tied to any return. Even though the client might have a SSN, the return can have an EIN. The client information screen controls the SSN/FEIN that the return shows. 

Look at the resources on this page https://proconnect.intuit.com/tax-online/resources/