First try: Seas0nPass ran all steps and said it was done.
When I connected the ATV to the TV I got the same 5.2 that was installed with no file modified (About Apple TV said 5.2 not 5.3).
Second try: I tried restoring with iTunes (using the FW created by Seas0nPass) and got an error.
Third try: Again using Seas0nPass and this time I think the process went fine. It said Done. Now when I connect the ATV to the TV, the led blinks fast and no system is loaded.
How can I fix this?