Not sure if you're using classic or new quizzes, but I got burned by failing to save in ALL the necessary places. Make sure you save the overall quiz *and* each question.
I had to re-enter a bunch of questions because of this -- good luck!
Make sure you click “Update Question” after each question. I also recommend creating a question bank first and then adding those questions to the quiz second. There are many benefits to question banks, but for this topic, a question bank may help you remember to update your questions.