According to user feedback from the external media MacRumors Forum and the Reddit community, some of the AirPods acquired from Apple Repair are in a non-upgradable state, running a firmware version of 2D3, while unofficial channels have firmware updates. It is also not possible to pair with airPods that have not been replaced.
Apple pushed the unusable 2D3 firmware to the AirPods on or earlier than March 25, so some customers have been unable to use AirPods for weeks.
One Reddit user responded: “I’m having the same problem. The AirPods on my left side were repaired for AirPods with 2D3 firmware, and then Apple replaced the AirPods on the right, which i can only use alone with them now. “
In fact, there are also many questions about 2D3 firmware on Apple Support Forums in China, such as a user who wrote on March 27 that “AirPods headphone firmware 2D3 cannot be upgraded” and the earliest questions about 2D3 firmware appeared on March 13.
There is also a lot of discussion about 2D3 firmware in the B-station review: