The navigation drop down list does not work.

I would like the drop down list to only allow the user to jump to slides the previously visited.

Any help would be greatly appreciated.

It does work just not in the way that you want it to without changing a base setting for the modules navigation.
If you want users to be able to re-visit previous pageswhile only being able to progress to the next frame in any sequence of frames then:
Goto the drop down MODULE
Select RUNTIME SETTINGS
Select the RUNTIME tab
Select ALLOW TO VIEW SLIDES IN SEQUENTIAL ORDER ONLY
This will give you the funtionality you are after.

This is SCORM strict navigation.
There is also a device called TASK CONTROLLER which can control SCORM complex navigation. However it is one of the least documented features and even the dev team say it's tricky to use!
This would allow you to use different pathways through the module.
For example you start with a simple pre-test if the user fails that then they cover the area they lack knowledge on. If they pass they skip past this area.
You can do this kind of thing 'by hand' but it is a pain to work sensibly and managing the scores through variable pathways is tricky.