By default, courses generally have completion tracking enabled, but the criteria for completing a course has not been set. If you need to track completion of courses (e.g. get a green check mark), you must set the course completion criteria. The criteria can include meeting completing an activity's minimum grade level, getting a "passed" or "completed" message from a SCORM file, or even manually ticking the checkbox on the course outline pagean overall course grade and/or manual completion, but you must, at a minimum, select something in the page below.
To set the criteria for course completion:
...