I know this thread is super old but I just wanted to say, I encountered the same issue, because I am using the windows dfu-programmer I thought it was because of that, but it turns out I was typing it slightly wrong each time which is odd because I sware I typed each letter individually, but copy and pasting the command from here to cmd worked, then I got Error on line 1, not error parsing line. And to resolve this I opened the raw file on github of the firmware and copied it to notepad and saved as all files .hex, that seemed to work. Just wanted to say just encase someone who is also trying this on windows stumbles accross this thread from google like I did :)