Currently activity completion tracking is not working for Big Blue Button.
The activity completion tracking settings are as follows (found at the bottom of the activity settings page):
Completion tracking: Show activity as complete when conditions are met.
Require View: Checked for "Student must view this activity to complete it"
I enter the activity as a student,stay in there a while,type some data, and then exit. When I return to the course the activity is still not marked as complete.
It doesn't appear this Moodle functionality is currently working with the Big Blue Button Activity.