mobile

I need some help, I installed a rooted lollipop 5.0 because my current 4.4 was buggy. Unfortunately lollipop 5.0 was even worse. Now I am trying to flash back to stock using odin, but I can't find kitkat 4.4 only 4.2 and I tried flashing to that and I keep receiving Auth- fail. So now my phone is soft bricked. I can only access download window and the recovery. I tried everything I cant get back to 4.4 nor lollipop 5.0 so please advice what to do. I I can get a download for kitkat 4.4 I would try flashing that maybe that will work. I have a at&t galaxy s5.