How to reset a trainee to retake training and quiz?

I have a course that contains a PowerPoint/Presenter Training and 5 question quiz. There is some issue that is preventing some trainees from conitnuing after they select an incorrect answer in any one of the questions. They cannot move forward or backwards. Once I can determine what the issue is, how do I reset these people to be able to make another attempt at the course and quiz. I have set the quiz for 3 attempts.

I have had other situations in the past where I could not determine how to reset a person, to try again. This would be very helpful to know how to do this. I don't want to override their score, because they have not demonstrated that they can complete the training.