Without assuming the worst, and thinking that students have not done their work, it is always good to check the following things and explore all options:
Is the student using the correct account, with which he also has access to the material?
Does the learner have a stable internet connection?
Is the learner using the most recent version of the app or browser?
Is there any software running in the background, such as ad- or pop-up blockers, virus scanners or parental software, that could potentially interfere with LessonUp's operation?
In addition, it is also good to have insight into the student's progress in LessonUp:
Does this happen only in single lessons, or are results not visible in multiple lessons?
Does this happen in all subjects in LessonUp?
Furthermore, the reporting of the lesson in LessonUp provides valuable information:
The student already started the lesson?
Does it say: time 0:00? If so, the student has either not started or has been offline during the creation of the lesson.