Flashing dfu file for M3 gives error: invalid firmware file. What am I doing wrong ?

[asp-q]

My device is recognized. I use the following firmware files. But I am unable to flash the older firmware versions.

• bose-dfu-v1.1.0-win-x86_64.exe (from https://github.com/tchebb/bose-dfu)
• M3_1.0.X_stack_plus_app.dfu, X = 6, 8, 13 OR M3_1.0.13_ext_signed**.xuv**

I run the bose-dfu in a command prompt, I follow the instructions as mentioned. First, enter-dfu, then download firmwware file and then leave-dfu. But it does not work. I have tried all the files dfu and xuv. It always gives than error
**Error: invalid firmware file

Caused by:
DFU signature is not present; are you sure this is a DFU file?**

See screenshot below. Can someone tell me what I am doing wrong ?
@tchebb The initial issue was that my device has red flashing light. I could not use the bose-updater (latest file from you) even with the js trick (#35). Then I resorted to brute force flashing the device using bose-dfu. Any help will be greatly appreciated.