I am experiencing the same issue that the user charsv5 has reported in the closed thread below. When I click “run” it takes a very long time for the site to respond (around 2 minutes) and then I see a red cross, even though the code is correct (e.g. I am on the last exercise, where I do not need to enter anything new, but I am still not able to proceed).
I am experiencing the same problem on Google Chrome, Firefox, and Safari and I have the latest MacOS installed. The previous thread has been closed since you were not able to reproduce the problem, however, I was wondering whether there are any updates on this issue?