First, check to make sure that you are indeed online. For example, go to google.com and do a quick search. If you are online and this problem persists then refresh the page in your browser. If this does not fix the issue then restart your device. On devices such as those running Windows or iOS, when a browser partially crashes it can sometimes require a system restart to restore its functionality.
In general, it is a good idea to download and use the Chrome browser.
If your problem continues to persist after the restart, please contact support at https://quizster.co