It would help if you could please post the challenge name or better yet post the url to the challenge. In the future you should try using the Ask for Help button on the challenge, so these things get auto-populated in the thread.
Thank you.
EDIT: I found the challenge you are asking about. Your code is correct. Try refreshing the page or using a different browser before running the tests again.
Ii suggest testing all of this on Chrome instead of Firefox. Also, if you open the browser’s console (Ctrl + Shft + J in Chrome), do you see any error messages?