Lately we've had a few reports from users who are unable to progress toward mastery even if they get their 3 or 5 questions in a row correct. Correct answers do light up the score circles in green, but 3 in a row or 5 in a row does not promote towards mastery. Instead the user is offered more exercises.
The issue has been reported to the troubleshooters who are working on it. However, if you are seeing this problem, please send a Help request stating which exercise you are working on.
We apologize for the problem. As of now we can only recommend that you work on other exercises while this is being fixed.
June 28th 2016