I purchased the Galaxy S5 back in April and now I am selling it so that I can purchase the LG G3. The problem is I'm trying to flash back to stock with Odin and it won't work. I downloaded the stock firmware from Sammobile and loaded it into Odin, put my phone in download mode and hit start and it says "fail." I can't get it to flash. I'm rooted but I haven't installed a recovery or custom rom. Any guidance would really help. I have no idea why I'm getting fail errors.