Cannot apply for online self-assessment

Hi, I am having trouble applying for a self-assessment online for capital gains. My application gets rejected with info over email as titled "Action Required: HMRC Application Rejected" and error message being "We are unable to process your application because the address provided does not match our records.". In there there is advice to "You will need to check or update your address before resubmitting the form.", but after calling HMRC, the lady on the phone told me that there was nothing wrong with my address and it's exactly the same on the system as what I've been inputting so far. She said that perhaps it could be due to the country being listed as "Great Britain" instead of "England"? What can I do in this situation since the online form doesn't work? Thank you.

Hi,
This forum is for general queries only and is intended to help you self-serve. We are unable to provide specific advice tailored to individual circumstances.
You may wish to contact our team for advice
Self Assessment: general enquiries
Alternatively you may want to seek professional advice.
Thank you.