Cannot jailbreak ATV2

This ATV 2 (was formerly jailbroken) model nr. MC572NF/A with software 6.2.1 on it installed refuses to jailbreak. When I use Seasonpass I get the message that there are critical errors and seasonpass stops. Is there any soluyion for this?

Windows finds device in DFU but while uploading iBECk66apRelesase.dfu gives error entering DFU mode device not supported

Exactly the same for me. I have tried on Windows and get the same error message that the device is not supported. I mostly try on OSX platforms. I only have a recent iTunes on all platforms though, and wonder whether this is the home of the problem. When using the latest OSX release and latest iTunes on it, I get the same error message as on latest Windows and iTunes: Device not supported. On earlier OSX platforms I get stuck at " failed to reset USB count."