Using Moodle 3.7 and performing a question from the STACK demonstration course I have found this
What i'm doing wrong?
Bernat.
It looks like you are doing nothing wrong! That is odd, if you email me more details of your setup we will get to the bottom of the problem and fix it.
Chris
Chris, I have reviewed the question and found the error: score at PRT was set to 0, changed to 1 make it works.
As I told you I had just imported the question from your DEMOSNTRATING STACK course.
https://stack2.maths.ed.ac.uk/demo2018/mod/quiz/attempt.php?attempt=51114&cmid=187&scrollpos=0#q1
There the error occurs also,