There is a bug where the validation function checks all quizzes on the page and will not let any quiz submit without all required fields being filled in all quizzes on the page. Meaning I see the “Please complete all required fields” message, when I press the start quiz button.
Just for info then am I running latest version of WordPress + latest version of your plugin.
If you take a look at this page “modul-4/” then you can see that it’s a general problem as all quizzes has the same problem with the “Please complete all required fields” message. I have noticed that the problem occurs as soon as you have more then one quiz on a page. If only quiz then no problem.
I just checked all the quizzes of this page from backend. As you have set all the questions to “Required” from Advanced questions settings, that is why it doesn’t let you submit the quiz without answering all the questions. Please disable the “required” setting for all the questions, then you won’t see this message again.
I have also attached a screenshot with my response.