What are your settings?
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EDIT: I see in your other post you're using per feedback range.
Case 1: multiple plays
Remember that the points is give only once, even if you allow multiple plays, so make sure that's not the case.
Case 2: reset game
Ok, check if you have records for this member in the quizzes_membersshop_points table. I just noticed that when you RESET GAMES from a quiz, I'm not deleting records from this table so the the user didn't earn the points next time he plays. This table was created to avoid people from pressing F5 or reload the page and earning same points over and over.
In my tests, clearing the table, worked fine.
@James101