How to set the max score for a quiz with categorized random questions?

Hi, i created a quiz with categorized random questions. The category has multiple choice questions and long answer questions. and user is able to take the quiz. But while evaluating the long answer questions, getting the PDO Exception error. I observed that the max_quiz_score is 0 and hence the score is not getting calculated and throwing the PDO Exception error.

How to set the max score for a quiz with categorized random questions?
Thanks in advance.