Different types of learners participate differently in an online class. Students can withdraw from an online class for a number of reasons. 

It is best to offer synchronous sessions with only one student. Asynchronous discussions can happen at any time. 

Instructor presence is important in an online classroom. Instructors should include a biography page. 

Most of my students have full-time jobs while taking online courses. Some of my students have children and families. Therefore, their biggest challenge is time management. They might forget to post their weekly discussion and so, I would send a reminder email before the week ends. My students are aware that there is no extension on discussions.