Manage fields not showing up

I need to add classes to the form made with Profile Builder. I have the appropriate add-on installed, “Custom CSS Classes on fields”, but there is no option to go to Manage fields on the Profile Builder tab. Thus, I am unable to add classes to the forms. Is this a known issue? All the respective plugins are active and loaded. How can I resolve this before I advise the customer to choose a different plugin to manage users!