mobile

I have recently tried to download Lollipop to my S4, which is currently running 4.4.4, but each time it hasn't work. My phone was previously rooted and I never actually installed any custom roms. I was able to unroot it, and my device status is now official, but Lollipop still won't download. Each time I have tired this, it has gotten into download mode and said in red on the top left hand corner of the screen that the phone could not boot normally and that it was in Odin mode. I really want to have Lollipop on my phone so any help or advice would be greatly appreciated!!