Jason,
We still have to make the effort to get them to connect with you. Certainly there are some that just "drop off" and refuse to communication with you; however, we should be making the extra effort in online courses to connect with these individuals (via phone, etc.) to determine what the problem is. It could be a personal problem, a technical problem, or genuine misunderstanding. Try to connect with them using all means possible: video conference, phone, chat, text, whatever means possible. Also remind them of the consequences for not communicating with you (possible failing grade, other issues) so… >>>