Unable to Confirm Identity on Government Gateway

I have been in the UK now for 2 years and have had my NI Number as per the correspondence received registered correctly. However whenever I try and confirm my identity it says my details are incorrect. I have written twice to the Self Assessment Service with certified copies my identification being sent on both occasions, when following up with the call centre months after, to be told to hang on for the Correspondence to be processed. This has been for more than 6 months now and I am still unable to log HMRC Tax because I am unable to verify my identity. HM Revenue and Customs BX9 1AS United Kingdom Please advise if there is somewhere I can call to confirm what detail is in fact incorrect as it seems my correspondence proving my identity is not being accepted.

Hi,

You would need to contact our online service team for assistance.

Technical support with HMRC online services

Thank you.