As I see it there are a number of points here?.
1) Was your original idea much too complicated, and they didn't consider you capable of completing it? - we see a LOT of those sort of questions on here!.
2) Was it too simple, not considered challenging enough, and turned down for that reason?.
3) I thought the idea of these projects was that YOU came up with the idea, and ducumented the entire process - even if you didn't manage to make it work, you could still pass.
Yopu've never mentioned what your original idea was, nor what you've now been given?, perhaps you might like to let us know what they are?.