Welcome to Vodafone Community
I too have this same problem with an LG G5 trying to go through the unlock procedure you have sent.
When I select "Service Provider Lock" from the menu I get the message "Your Phone is not personalised" with an option to "Dismiss" - I don't get as far as being able to enter the NUC you have sent me.
I assumed this meant the phone was not locked, I inserted the new SIM (Plusnet) but it still flashes up all the Vodafone details on start up and the new SIM does not work. I have confirmed that the new SIM is activated so there should be no problem.
Please advise, much appreciated.