I enabled developer's mode and installed SeaBIOS.

I created a bootable usb flash drive with dd if:/home/chronos/user/Downloads/install.iso of=/dev/sdaX bs=4M; sync.

I, also, enabled the second level of dev mode with chromeos-firmwareupdate --mode=todev

Finally, to have chrome boot into the usb drive I ran crossystem dev_boot_usb=1 dev_boot_legacy=1.

But, when I restarted the computer and did Ctrl+L, and chose the bootable drive with the installation files I got:

Select boot devices:
1. USB Drive PNY USB 2.0 FD 1100
2. MMC drive

Booting from Hard Disk...
Booting from Floppy...
Boot failed: could not read the boot disk

No bootable devices. Retrying in 60 seconds.

I do notice that it never says Booting from USB.

What is the problem?