Purchase option not shown to logged out users

Course Single page is not showing the option to logged-out visitors for purchasing course. In Enrollment section, I found that "Anyone Can Enroll" option is not available. Only "Registered Users Can Enroll" available.
In "Dashboard > Settings > General" section "Anyone can register" option is checked. In Dash > Store Settings > General > Misc. " section, Force Login option is unchecked. So I'm not sure why the visitors don't see the purchase button on courses. We need to investigate in details.