The global value for "max attempts" is 0 for the problems in question. They are not overwritten by settings for particular students.
I wonder how this could have happened. Maybe the instructor put in "0" there, because he thought that this might mean "unlimited", which seems not to be the case.
Maybe it might be worth to tell the instructor somewhere what is means if he enters "0" there. Maybe it would even be worth to show some warning (probably there are only a few use cases for the value "0").