I have the same issue with my S4, but Josh's method unfortunately didn't work for me.
This is what I did for about 10 times now.
I went into the recovery mode. Selected the wipe data/factory reset option. Selected Yes. It said Formatting data, then formatting cache and said data wipe complete. Then, I selected reboot system now. It rebooted, got stuck at the at&t logo after the welcome sound played. I waited 15 minutes hoping it would come out of that state, but in vain.
I will keep trying since deepak said 10 to 20 trials. But, really frustrated that even factory reset is not working.
This is what I did for about 10 times now.
I went into the recovery mode. Selected the wipe data/factory reset option. Selected Yes. It said Formatting data, then formatting cache and said data wipe complete. Then, I selected reboot system now. It rebooted, got stuck at the at&t logo after the welcome sound played. I waited 15 minutes hoping it would come out of that state, but in vain.
I will keep trying since deepak said 10 to 20 trials. But, really frustrated that even factory reset is not working.