Quizmaker dies ..with the click of FINISH

The problem: When I come to the end of a quiz and I click on "Finish", nothing happens.

OK, here is what I am doing:

In the "Pass Result" I have a link such as: https://course.xxx-driversed.com/abcdef.php

The php script logs the date and time when the student finished the quiz and starts the next lesson.

Now, there are some students in Nevada, where this does not work. The php script is not executed. Consequently the student cannot continue.

Here are some strange occurrences:

1. The same (very similar) scripts are used for moving from one lesson chapter to the next. No problems here.

2. The problem starts at the end of a quiz.

3. There are no problems with these scripts for students in California.

4. There were no problems with these scripts in Nevada until about 6 months ago.

5. Most students having a problem are living in Henderson, Nevada (Close to Sin City, OK that's Las Vegas, Nevada);

I am suspecting that parents have "child guards" installed. Although they swear up and down they have not.

Now, the question I have is: what code may be/is produced by Quizmaker that causes Quizmaker to be trapped in a child-filter system? 

I know this is a tough one. However, it is creating a very big headache. If I am right, this could open up a can of worms.

Thanks for all your help