I just went through the process of downgrading...sorry, "upgrading" my camera to XDCAM MPEG2. Used the new Sony website for that. Turns out, I could not work the site using Chrome browser, kept saying my session expired. Continued using Safari on Mac and all went quickly.

So if you have an issue registering and activating your 4K key on an X70, maybe don't use Chrome.

paul