Unable to Recover Android Things Device

I am unable to flash a new image to my Pico i.MX7D board because I cannot get fastboot to work.

It began when I accidentally flashed a production image to the board. Now I cannot get my computer to recognize the device. I followed the instructions on the Android Developers site to Recover a Device but cannot get the last command, 'fastboot usb' to work.

From the serial console:

U-Boot 2017.03-00007-g7f67ae9 (Jul 20 2017 - 17:31:24 +0800)

CPU:   Freescale i.MX7D rev1.2 996 MHz (running at 792 MHz)
CPU:   Commercial temperature grade (0C to 95C) at 27C
Reset cause: POR
Board: i.MX7D PICOSOM in secure mode
I2C:   ready
DRAM:  512 MiB
PMIC: PFUZE300 DEV_ID=0x30 REV_ID=0x11
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
No panel detected: default to EJ050NA
Display: EJ050NA (800x480)
Video: 800x480x24
In:    serial
Out:   serial
Err:   serial
flash target is MMC:1
Net:   FEC0
Fastboot: Normal
Hit any key to stop autoboot:  0 

=> fastboot usb
g_dnl_register: failed!, error: -19
exit not allowed from main input shell.

Other forums suggested the unlock command. Nothing seems to happen when I run it:

From the serial console:

=> fastboot flashing unlock
fastboot - use USB Fastboot protocol

Usage:
fastboot <USB_controller>
    - run as a fastboot usb device

=> fastboot oem unlock
fastboot - use USB Fastboot protocol

Usage:
fastboot <USB_controller>
    - run as a fastboot usb device

From my computer:

$ fastboot flashing unlock
< waiting for any device >

$ fastboot oem unlock
< waiting for any device >

Both 'fastboot devices' and 'adb devices' fail to return anything.

I also followed the i.MX7D reference guide to Set the Device into FASTBOOT Mode (section 11.2). Those commands failed to be recognized:

=> su
Unknown command 'su' - try 'help'
=> reboot bootloader
Unknown command 'reboot' - try 'help'

I found a post on another site for the same issue and had no luck with the recommended solution. I tried adding 'androidboot.dm_verity=disabled and androidboot.selinux=disabled' to the bootargs but it didn't get fastboot to work.

=> printenv
baudrate=115200
bootargs=androidboot.dm_verity=disabled androidboot.selinux=disabled
bootcmd=boota mmc1
bootdelay=3
ethact=FEC0
ethaddr=00:1f:7b:86:6a:81
ethprime=FEC
fastboot_dev=mmc1
fdt_high=0xffffffff
initrd_high=0xffffffff
loadaddr=0x80800000
splashpos=m,m

Environment size: 287/8188 bytes

Additional information:

• Mac OS High Sierra 10.13.4

• Device (Pico i.MX7D):

  U-Boot 2017.03-00007-g7f67ae9 (Jul 20 2017 - 17:31:24 +0800)

  real-arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)

  GNU ld (binutils-2.25-129dec3) 2.25.51.20141117

• Using Serial to view the serial console

EDIT: I have tested using another board (that was not flashed with a prod image) with my computer and everything works as expected.

NXP i.MX7D - image

• Now you can recover your device only with JTAG
• Connect JTAG to the PORT A as per the IMAGE and FLASH the required Firmware