Using the Wizarding World app, anyone who has previously been sorted on Pottermore or WizardingWorld.com will be able to re-take the Sorting Ceremony and discover their Hogwarts house. 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.
After this you can re-take the Sorting Ceremony as many times as you like, but the Sorting Hat will not change its mind and you will get the same house each time.
If you do not have access to the Wizarding World app, you will not be able to re-take the Sorting Ceremony on our website if you have already been sorted into your Hogwarts house.