Thank you for your answer.
Can you explain me how to run the regrade on the quiz?
It is one test divided into 4 "mini-quizzes". The final score is calculated on the base of the the 4 "mini-quizzes" scores. Do I need to run the regrade on the 4 "mini-quizzes"? I guess yes because the scores of all the "mini-quizzes" do not appear in the grader report and consequently the final score is missing too.