My (2011) UK passport rarely works in the UK automated passport gates, I think it also failed at the NZ entry gates - not a real issue though since you just get it checked manually immediately. I've not had any issues with VWP in the US, and I can read my chip fine using a phone. The gates just really suck at reading passports.
The N4 is a bit old, it's coming up on 3 years now I think. I wonder if there's a new NFC standard that this phone doesn't support?
I've heard that some passports are using a different NFC standard that most phones (even newer phones) don't support, I can't find any evidence right now though.