Go back and read my post here https://www.3dhubs.com/talk/thread/avatar-iv-qidi-tech
My report on a successful upgrade to Sailfish 7.6.
AVR Studio won't work. You need to use AVR Dude command line.
Read the thread and follow the links I posted and read them closely before you try.
You will need the Hex code for Mightyboard Rev E.bootloader.
Good Luck