Have you tried manual rescue where you press rescue and then plug in the USB?
That is required for what I was suggesting (safe mode, etc).
If all you get is LED slowly fading in and out, you may not have firmware, just a boot loader and again you need to start with it unplugged, and press "upgrade and erase", then plug it in. If that doesn't work, you either need a bootloader or you have a cable or PC problem.