If exercises do not work or there are other problems with the website, try reloading the page as follows:

Mozilla Firefox or Google Chrome

1. Go to the page where the problem occurred
2. Hold the Ctrl key down and press F5 at the same time

Apple Safari

1. Go to the page where the problem occurred
2. Hold the Shift key down and click the "Reload" icon at the same time

If force reloading does not fix the problem, try removing stored cookies and date.

Here are a few links with instructions for how to do that on different browsers:

Safari: https://support.apple.com/guide/safari/manage-cookies-and-website-data-sfri11471/12.0/mac/10.14 

Chrome: https://support.google.com/accounts/answer/32050?hl=en

Mozilla: https://support.mozilla.org/en-US/kb/how-clear-firefox-cache 

Make sure your browser is updated to the newest version. You can also try another browser if possible.