I am not sure what you mean by validating the new SIM card. I followed the instructions with the card , the phone accepted my pass word but gave the error message "SIM not valid". Putting old SIM back the error message was "SIM registration failed". Trying the new SIM in my newer second hhone means reducing its size. I can try this if you think the new SIM will never work in the Nokia.
I have done most of the things you have suggested and the phone still says the SIM is not valid and is inoperable.
I tried looking at the network settings procedure via the link you supplied. My phone model was not shown and after entering the IMEI number , I got a message "Sorry your device is no longer supported".
Can you suggest any next steps?
Thank you very much for the support you have given.