The message you are receiving means that the demographic details you have entered in the registration process (Name, Surname, Date of Birth, Address, NHS number) does not match the details the NHS has for you.
To check your NHS number, you can visit the following page:
Please let us know if this is the same as your NHS number on your GP record or not.
If any of these details are incorrect on your medical record then getting in touch with your practice is the only way for this to be rectified.
Please note that if your GP details are correct then the only thing left to do would be for your practice to synchronise their records with the NHS database ("Spine") in order for our service to receive your correct details.
Please also note that once the synchronization is complete, it can take up to 48 hours to update within your NHS account. Sign out and back into your account to re-fetch the updated data and make sure the update has been successful.