Updating full rom firmware failed on my panther chromebox, now it is bricked

I have been using MrChromebox firmware for years on my ASUS Chromebox CN60 M004U ( panther ) running archlinux from the very first day but today when I tried to update full uefi rom 2405 release to the latest with the script it failed to update then I foolishly rebooted. Now it powers up but no bios splash screen, nothing. I did read the docs but it is not clear how to proceed with unbricking.
Firstly I would try performing an EC reset as the docs suggests, but my panther has no reset button so I need help how to recover my chromebox bios firmware.
I have frequently updated full uefi firmware during the past few years with no issue, so it is quite strange why it failed now…
Any help appreciated thanks

Unfortunately your device lacks cr50 ccd support, so the only way to unbrick would be with a programmer: