They are going to be emailing everyone who subbed with feedback on their submission over the next few days and they've got another submission window open to everyone starting on Monday so don't give up too soon! Finish polishing a different manuscript ready to sub to them next week then be prepared to take on their feedback on your manuscript, act on it, edit and try somewhere else... it's not often that you get feedback on your submission from a publisher so grab this opportunity with both hands!
This is copied and pasted from the email they sent to everyone yesterday:
Our next submission window is opening soon!
From the 13th of August - the 30th of September our submissions will be open to EVERYONE. Anyone who has written a book for children and Young Adults is free to submit their writing during this window, using the guidelines on the 'Submissions' section of our website.
We look forward to seeing what you've got to share with us!