If you have not configured any completion criteria for the course, then Moodle has no way of knowing when you are expecting it to mark the course as "complete", so the course will never be marked as complete.
There is plenty of documentation on how to configure course completion in the Moodle docs: https://docs.moodle.org/en/Course_completion
There is plenty of documentation on how to configure course completion in the Moodle docs: https://docs.moodle.org/en/Course_completion