No.
There is no requirement to serve a NIP for a mobile phone offence, and therefore no defence from a failure to serve a valid NIP within the 14 days.
Currently, you have been served an s. 172 requirement, which contrary the title of your thread, you do not need advice regarding as you have, from what you have told us, complied with your obligations in respect of that request. Whether a subsequent corrected s. 172 requirement will follow, or whether they will simply drop it out of embarrassment, is anyone's guess.