I already figured it out. I have the newest model, the A6400A, which is a 2025 version with firmware 1.0 — but that’s actually the latest firmware, equivalent to version 2.0. It includes animal tracking just like the 2.0 update. So it seems to be a mistake on Sony’s side. That’s why my PC recognizes the camera, but the software doesn’t, since the camera is already up to date.

I assume you've read through all of this, but in case not: ILCE-6400 System Software (Firmware) Update Ver. 2.00 (Windows) | Sony USA When someone is experiencing trouble updating firmware it's usually some small niggly little thing that they missed in the translation. We seem to focus on the big stuff. I'd start over and do everything they say.

I bought my A1 grey market from Panamoz. No problems with firmware in the US.