We recommend clearing your browser's cache and cookies before starting a quiz in D2L. You can find browser-specific instructions how to do this here: How to Clear The Cookies and Cache in Popular Internet Browsers (link).
The quickest solution to most quiz issues is to close your browser and re-open it, then re-launch the quiz. Your progress should be saved and you will resume where you left off. Contact the IT Service Desk if the problems persist.