How long is the delay for my HMRC account to show up to date N.I. Contributions

I paid missing gap years 2021/22 and 2022/23 in January 2024 but the payments are not showing on my HMRC account. Why is it taking so long? The two missing gap years were paid together. I entered the relevant information as per instructions so HMRC could identify my HMRC account but they are not showing up. Why? Should I write to National Insurance Contributions and Employers Office? If yes, what information should I include on my letter to them? is it safe to include my N.I. Reference No. ?

Hi Nick H,
Sorry that your payment is not yet recorded on your National Insurance account.  May I ask that you call the National Insurance Helpline on 0300 200 3500 (from the UK) or +44 191 2037010 (from overseas) and they will be able to help you further.  If you could have details of your payment when you call then this might be helpful.
If you would prefer to write, please include your name, address and National Insurance Number.  Include details of your payment (bank account and sort code number) and the 18 digit reference number used.  
Our postal address is:
HM Revenue & Customs
PT Operations North East England
BX9 1AN
United Kingdom
Thank you.