I had this problem: https://wplms.io/support/forums/topic/questions-are-not-displayed-in-course/#post-79129
Then it was marked this as solved - maybe me and i forgot, I'm not blaming anyone. The point is: it's not solved. I can see the questions when taking the quiz, but some questions I can't acess unless I click on the last question, then click on previous question. And one question I can't access at all.
The questions are: 11, 12 and 13
Link to quiz: http://educative.com.br/quiz/introducao-florais-de-bach-avaliacao/
My credentials are in the post link above. Also, some of the users still can't see any questions. It's just on this quiz. I have no idea what we did wrong.
As you can see questions are displayed perfectly ok.
I wasn't able to replicate the issue on your site.
http://prntscr.com/d9y8fs
http://prntscr.com/d9y8ve
It is advise that you clear your cache and check again.