Hi Melissa
OK you can still check that learners have the default settings under graded roles and show gradebook to students , yes under site administration.
Is the Quiz a Totara quiz or a SCORM object if it is a SCORM there are publishing settings in the SCORM that need to be correctly done.
Other things to check are does the user have two roles trainer and learner - and check quiz is being submitted.
I can't think of any other things that might be causing this but there probably are.
Craig