"Nothing to pay" message but NI owing, and ....

Hi all ... As in the subject line, I have a small amount of NI to pay (£340 altogether for class 2 and 4) but no income tax to pay. How do I know that paying this amount to the usual HMRC account will be assigned to the NI? And .... When I check back through my NI, the last six or seven years are listed as "incomplete" and have a note saying something to the effect of "we're processing this. You need do nothing." I know that I can I ly top up NI for the last six (?) years. I think this message has been in place since at least 2020 (first noticed during the first lockdown when HMRC humans basically inaccessible!) so it looks as if I will continue to be, in effect, blocked from topping up in future, if this six year "processing" continues to move forward. Am I missing something?!

Hi Executor one,
If you contact the self-employed helpline or use webchat services via a Personal tax account, you can discuss your position.
They will advise you on the tax years and the national insurance for any shortfalls you may wish to pay or review.
If you are paying the class 2 & 4 through your self-assessment, we will be expecting this payment to be received and in due course allocated to your national insurance account.
Phone Number - 0300 200 3500
Open - Monday to Friday: 8am to 6pm, Closed on Saturdays, Sundays and Bank Holidays.
Thank you.