Edit: I read a little bit here https://github.com/Proxmark/proxmark3/wiki/Kali-Linux#possible_error. I'm assuming you successfully flashed the bootrom so after that the Kali guide says:
"Upgrading Proxmark3 Firmware
Make sure you are in the "proxmark3" directory and issue the following commands:
cd client
./flasher /dev/ttyACM0 ../armsrc/obj/fullimage.elf
cd ..
The flasher program will detect your Proxmark3 and reboot it. Once it reboots and starts back up in the proper mode the flasher will detect the Proxmark3 again and then start flashing the firmware. You may have to run "dmesg" and check what serial port your Proxmark3 is connected to and replace "ttyACM0" if you encounter issues. Also try unplugging and plugging the USB cable back in and running the command again. WARNING! Do not unplug the USB cable or cancel the command while it is actually upgrading the firmware. It may take a little while for the flasher to actually detect the Proxmark3 after rebooting, typically less than a minute."
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