I recently got a new iphone. Cell provider assigned a temporary number to facilitate cloning of old phone to new. Reassigned original number to new phone. Two-factor authentication now fails on Password Manager even though it works when logging into the Norton website. I tried turning two-factor off but it continued to attempt to send 6-digit number to mobile. Went back back in and turned it on. My mobile number appears in set-up but still does not receive text messages from PW.
Your thread title mentions 2FA, but it sounds like you are referring to the Mobile Unlock for Norton Password Manager. As you found, it is not tied to the phone number, and changing to a new phone required setting up the feature again.
Resolved! I was able to reinstall PM on my old phone and determined that texts were being sent to that phone instead of my new phone. Norton uses something called the MID to identify the phone and seemed to be fixated on the old MID instead of picking up the new one. I removed my phone number from the device list in PM; then re-added my phone number. This time it replaced my old "MID" with the one from the new phone. Problem solved! Too bad there is nothing, at least that I could find, in the doc about the MID.