Check how to access it again. If you have signed up for a ShopBack account with email and password. Try checking your email and password again. 

If you have signed up for a ShopBack account with Facebook:
Select "Continue with Facebook".

If you have signed up for a ShopBack account with Apple ID:
Select ''Sign in with A

If you require any further information, you can contact the ShopBack Help Center through friendly live chat agents LiveChat! or through e-mail at  ShopBack Help, every Monday - Friday from 8:30 am - 6:30 pm (except public holidays).