I'd like to change the business code for self-employment business income, but I don't see where to edit it. How can I change the business code?

When filing my Massachusetts State tax return, I got this error, "The return could not be processed for E-file due to missing information on Massachusetts Schedule C. Main Business, Principal Business Activity Code (PBC), and Business Address are required for electronic filing. Enter the required information on the Federal Schedule C and it will automatically complete the Massachusetts Schedule C." All that information in present in the Federal return I thought I'd try to change the business code (It's just the general, generic code currently) to resolve the error. When I try to edit the business details, I can edit all other details except the Business code. Any insight would be helpful. Thank you.