Hi,
can you please try to create a text document with the following content:
author = "YourName"
customer="Example"
; This is an comment
[Files]
; This is the NBootloader
StepStone=C:\Users\Admin\Desktop\pc1boot_31.bin
Please correct the path to the nboot if necessary.
Save this document with the ending .nbi. Then select this file and try the download again.
Your F&S Support Team