I have learned that communication is key here.  I have ran into this before at other institutions when technology breaks down or sometimes it is simply "user error." In the event of this happening, I am usually aware of when someone logs off via Zoom and I have sent quick emails to the student to further investigate what happened; pending the student is missing longer than expected (i.e. lost internet, took a phone call.)  I have learned that email is my best friend in this case, because I have had to adapt and redirect assignments because of it.