The Sorting Ceremony in the Harry Potter Fan Club app includes a new Augmented Reality Sorting Hat.
If you have previously been sorted via Pottermore or the Wizarding World website, but never within the Harry Potter Fan Club app, you will be able to retake the Sorting Ceremony in the app.
If you are sorted into a different house, you will be able to choose either your new house or to keep your existing one. You do not have to change your house if you do not want to.
Once you have been sorted within the app once, you will be able to retake the Sorting Ceremony there as many times as you like, but the Sorting Hat will not change its mind!