Apple is shipping single replacement AirPods with an unreleased firmware
(iMore iPhone)

What you need to know Apple is shipping single AirPods with a new firmware - 2D3 -installed. AirPods need to run the same firmware as each other to function. The first AirPod can`t be updated because firmware 2D3 hasn`t been released yet. People can`t use the new AirPod with their old one. If you have a faulty AirPod and Apple sends you a new one out, cross your fingers. If the replacement ships with firmware 2D3 installed you`re going to have a problem. That`s because firmware 2D3 isn`t public yet - preventing you from updating your existing AirPod to match. And as it turns out, that`s a problem as many people on Reddit and social media have found out. AirPods need to be running the same firmware in order to pair with each other, and because firmware 2D3 isn`t available, updating to it is impossible. That leaves one AirPod running an older version of the firmware and no way to sort the problem out. Not even if you reach out to Apple, as one Reddit user discovered. I`...