Cannot flash Intel nic: "invalid image file"

[jgarr]

I'm trying to flash an intel nic with iPXE. I have been following the docs and got my nic ID (80861502) made the rom, downloaded bootutil, booted freedos but the -restorimage command fails with the error "Invalid image file"
I found on the forums to check the ROM image size and I can see the rom created from make is 65K which appears correct and I also saw recommendations to try older versions of bootutil. I tried versions 18.3, 19, 20, and 21 and all give the same error. I haven't tried flashrom but am begining to think there may actually be something wrong with my rom.

How can I verify I have a good image and does anyone have suggestions for where to look next to get the rom flashed?