Adding Learners to a course

Are you speaking in regards to a retired instance of a course, one that has passed the deadline to complete?

If so, you can create a new instance of that course and enroll users into that new instance. Do so under view course > instances > +Add New Instance. From there, simply click learners under the course, change the instance to the new one you created, and click enroll. Select the learners and you are good to go!

I do this all the time.

I actually have a Learning Program with multiple courses inside. As new people request the course - I add their profile to the Program and let Prime take over from there. This has worked for me now for over a year.

So in my case many people have completed the course and many are still working on it.

Do you perhaps mean something else?