"Find your National Insurance Number" not working

I'm trying to find my NI number. I am from South Africa, and was in the UK studying in 2021-2022. I applied for an NI number in that period. Now I am returning to the UK, and need my NI number for my visa, but I cannot find it anywhere. I've tried the portal here : https://www.gov.uk/find-national-insurance-number - I log into the Government Gateway - It says "Confirm your identity to get your National Insurance number online", and lists passport as an option—which is what I have access to. - Then "We need to check your identity" - Asks for my name and DOB - "We will ask you about your National Insurance number" ... - So I select "No, I have lost or forgotten my National Insurance number " - It asks about my postcode, so I provide the address I last stayed at in the UK - "We need you to confirm your identity", and "international passport" is listed as an option - But because my passport (from South Africa) is not "biometric", none of the options work. What should I do to get my NI number?

Hi Callum,
If you could call our National Insurance Helpline then they will be able to help you trace your National Insurance Number and arrange for it to be sent to you by letter.
National Insurance: general enquiries
Thank you.