Social Security number not valid

I have received my social security number from URSSAF on my Notification d'Affiliation dated 21st September. It is a 13 digit number followed by 2 and starts with a 1 as per the previous response by Roxanne that a permanent number needs to start with a 1 or 2. It is not a 7 and so therefore is not temporary. However when I try to set up my Ameli account using this number I receive a message saying it is not recognised. When I spoke to a lady in the English helpline she said I needed to register as self employed on cfe.urssaf.fr but I already have set up my ursaff account so I am at a loss as to what to do next. I need to send the permanent number and my Attestation de Droit to the Insurance company within 40 days so that my to up insurance is valid. Please can someone help as I am going round in circles here and it is very frustrating?