VAT Registration

Hi,
I just became VAT registered in the UK, I submited my VAT number in seller central, and after being approved I get an email a few hours later saying that my VAT registration details have been rejected.
After several attempts of this happening again and again I realized that I can’t update my business registration number on the vat registration page (on seller central), as it comes back as an invalid number, although it has been verified before by amazon and it is the number shown on my business incorporation certificate from HMRC.
I have contacted Amazon for help numerous times but as usual no ideal response.
Can someone please help me out?
Thanks