What's wrong with Challenge 48

I went through all 250 levels in the campaign and don’t understand how to complete this task. I already tried to go through all the levels in the third chapter of the second book.

Hi DarkRyze, we’re looking into this issue. It would be great if you could share with me your user ID in a private message so we can troubleshoot your case specifically. Apologies for the inconvenience and thanks so much for reporting this!
Best regards,