Each state has its own regulations about what will happen if a quiz or exam is failed. Most will allow students to repeat a chapter without restarting the timer when it comes to quizzes; however, if a final exam is failed, some will require the course to be restarted as well as the timer. Please see your state's page on the course website for more information.
Also note, regardless of state requirements, students can complete the course up until the expiration date, details of which can also be found on the state page. Once the course expires, there is a limited time option to pay for a 30 day extension; When this course expires, you will need to repay and restart the course.