I dont know what's wrong with this, I think that nothing's wrong on this code:?
We need to see your code. It could be a known issue with the platform, that has been reported. The workaround so far is to refresh the page immediately after pressing Run. Don't wait for the lesson check. Run...Refresh...Run again if not marked correct.
This issue is related to vanishing content from our work. It is not lost, and does show up on refresh. This leaves us two options: Wait a few days, or get into the groove of refresh. The module can be completed.