The progress bar depends on the type of activities included in the assignment. Some activities are designed only for practice and do not generate a score.
For this reason, even if the student has completed all the activities, the bar may not reflect 100% progress.
These non-scored activities will eventually be blocked so that they do not interfere with the formal evaluation of an assignment.
Suggestion: Check that the activities within the assignment are gradable if you want them to contribute to the total progress.