How can I enable the bar at the bottom of an online assessment to allow my learner to go back a few slides?

Leaner has launched Captivate online assessment from Prime and is trying to go backwards to see a previous slide… the bar at the bottom does not allow learner to go backwards… how do I change this?  When we go out of Prime and launch the assessment again, it resumes in the same place.    In Captivate within the skin editor, all options including rewind are checked…