If you have time left in your attempt, close the attempt and then re-enter it.
If you still encounter issues, close your browser and re-enter the quiz in another browser.
If these options fail to work or if you are concerned about time in the attempt, contact BOLT Support right away. The sooner they know about the problem, the sooner they can help you resolve it. You will also have record of technical difficulty for your instructor if you need it later.