You no longer need to request unlock support. Read below.
Except for the introduction quiz, Each test that is graded automatically requires a score of seventy percent to pass. The introduction quiz requires a score of 100%.
For all quizzes that are graded automatically, the quiz will lock for two hours after two failed attempts. Please allow this time to review the content before re-attempting the quiz. You must wait 2 hours between each failed quiz attempt after that. Your quiz will open automatically when the time elapses.
In summary, you can take each quiz two times without a time penalty. After that, you must wait two hours between each attempt. The course was designed this way to prevent students from clicking through the course without taking advantage of the content. Your quiz will open automatically when the time elapses.