<Below this line, in what way does your code behave incorrectly? Include ALL error messages.>
I do not know where the app.js file is located on the page. The file icon is faded as well as the open editor button in the right window.
I was having the same problem. I found that if I clicked on the “Learn ReactJS: Part I” link in the middle of the top of the page, and then click back to return to the page, it seems to solve the issue.
HI. I am still having the same problem. how to resolve. The below comments did not solve the problem for me. where is the app.js file , and how to unlock the 3rd lesson, The mystery revealed one.
Check the top right hand corner of your screen, the 3rd symbol in (left of the notification “bell” and your profile pic) should be a little green dot; which if you hover over it shows “Connected to Codecademy”.
Click on the learn Reactjs link at the top of the page.
Then when you return to the reactjs summary. i clicked the continue button and it seems to work now!
I believe this is a connectivity issue. To the left of your avatar at the top right of the course page you should have a green dot indicating you are connected to codecademy. Occasionally the coding window (app.js) becomes opaque when the connection is broken. Keep reloading the course and eventually it comes right.
I am having this issue every time that I load a new page of the course, even if the green dot shows that I am connected. The only way round it is to go back to the course home page, and then reclick the green ‘continue’ button.