i've tried every solution I can find before posting, so here goes:
I've got an ATV2 that I had previously jailbroken, and had no issues. I had to restore it recently, which installed the latest firmware. No problem, downloaded the latest version of Seasonpass and started the jailbreak. ATV2 gets into DFU mode with no issues (though I did have to use the powercable), and is detected by Seasonpass with no problems. It fails every time at the "firmware install failed" box.
I've tested 3 different micro usb cables, and just to be sure, I downloaded and installed an 5.30 ipsw file and flashed it to 5.3 using my normal cable with no issues. I've downloaded the earlier 9.3 version of seasonpass and tried that, didn't work either. My theory is, because I can't find the file, is after the message that the jailbroken firmware has been created, the file hasn't actually been saved to my Mac. I've looked in Library, and also Documents ->Tethering, and can't find a firmware file created today. Thoughts?
ATV 2 is on 5.3
Mac OSX is on 10.11 (yosemite beta)
both usb ports tried
tested with and without power cable
tested 3 different micro usb cables
boots into 5.3 fine.