Player Navigation Buttons unavailable when reviewing quiz

Here's how the default, built-in quizzing functionality works:

• When the user takes (or retakes) the quiz, the program automatically hides the Next and Prev buttons.
• If immediate feedback is provided, the Continue buttons on the feedback layers hide the layers and then jump to the next slide.
• If there's no immediate feedback, the Submit button jumps to the next slide. 
• If the user reviews the quiz, the program automatically shows the Next and Prev buttons (even though they aren't selected in Slide Properties).

As you've discovered, when you select the Next button in the Slide Properties of a question slide, that allows you to control it with triggers. 

Without seeing your .story file, it's hard to say why your trigger to show the Next button during a review isn't working. It might have the wrong "when." It might be in the wrong location. (Triggers run in order.) It might be some other issue. 

Here are the best practices for uploading a .story file: 

• Only include slides that are related to the problem.
• Be sure objects, layers, motion paths, and variables have meaningful names.
• If there is proprietary content, replace or delete it. For example, replace proprietary text with “ipsum lorem” text.