Why is Siren is not recognised?

I initially registered my business via auto-entrepreneur.urssaf, but chose the wrong APE, which led me to the wrong CFE. I did get my SIREN but then URSSAF rejected me from the micro-entrepreneur regime as my (incorrectly) chosen profession didn’t qualify.

On your advice I contacted the local CCI (I sell used cameras online), and I’ve now had a meeting with them to correct the above. I think I’ve managed to re-register the business with them (they told me to expect my extrait K-BIS within ten days), but I’m very stuck with the rest.

The CCI told me register online at URSSAF to set up my cotisations and at imports.gouv.fr for the tax, also to register with the SECU. None of this is possible as my SIREN is not recognised and I have no social security number. The CCI told me the existing SIREN number would be valid but it appears not, I wonder if it was cancelled when URSSAF rejected me?

In three months since first registering I’ve had the SIREN letter and one from URSSAF (the rejection letter), and nothing else at all relating to my business, tax or social security. Is this normal? I’m not in great health but access to the healthcare system still seems as far away as ever.

Can offer any advice on what I should try to do?

Kind Regards
Matthew