Build a Markdown Previewer: Help and Feedback

Help i don’t understand why it doesn’t show up on codepen:
but shows up in codesandbox:

Also i keep getting error: marked is not defined and the tables are not showing up, the marked documentation lacks some instructions how the markdown works, here’s the full page view in code sandbox: i think i got it right but keeps getting errors.

Your code so far

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.103 Safari/537.36.

Link to the challenge: