If a student is unresponsive, start phone calling that student and/or that students' parents weekly.
Teachers should change Course Announcements often to keep engaged and coming to their online class (sticky factor)
Hold regularly scheduled office hours every week.
This can be set up as a Chat in Moodle and labeled, Teacher "Chat" Office Hours with the day and time. Students can also receive points for attending. You could also create a Chat of the week topic course related.
Create a Pacing Schedule for your course and make sure the students print a copy for themselves. They can check off assignments as they finish them.