He, some versions of the Z3 are getting the N(!)[1]. I'd say it's probable that it's your carriers fault, the Marshmallow updates for the Z3 have been out for a while.
I've an unlocked phone, so in my country I'll get it before those with phones locked to a network. You can use sites such as xpericheck.com to confirm that currently 7 locations have MM on the D6603 variant of the z3 phone.