When publishing a course, the Admin has the option to either make the course 'Private', so that only those targeted users can access it, or make it 'Public' so that all users on the platform can access it.
It's possible that this feature may be 'ticked' and 'greyed out' as soon as you access the Course Publish area.
If this is the case, it's due to the fact that 'Show Anonymous Responses' has been enabled within the 'Company Edit' area.
For further information on how to enable/disable Anonymous Responses, please see article: Courses - Anonymous Responses