The student's Entered answer matches the Answer Preview, and the Result is correct, but the student got 0 points for this problem, and it is marked as incorrect in the list of Problems on the left.
I looked at the student's responses in the problem set, and I could see the answers they entered for the other problems, but not this one. The answer for this one is blank, though there is a timestamp for when the answer was entered.
How can this be fixed? What could cause this?
Thanks for any help, and let me know if there is any more information that could be useful. I'm pretty new to WeBWorK and don't use it myself, so I have limited familiarity with it outside of creating courses.