I was not able to recreate your issue. I was able to view both of the quizzes and provide the correct answers for all questions.
Perhaps this is a caching issue, please do the following:
• Log out of all Pega sessions
• Close all browser tabs/windows
• Completely clear browser cache and cookies
• Restart browser and retry access via academy.pega.com
• If issue persist try incognito mode or/and different browser