RPi4B Booting from USB

I have installed LibreElec, but when I try to boot it, nothing happens. I think I have to edit the cmdline.txt file, but I am not sure what I need to put there to make it boot from the USB drive. I would appreciate any help. Thank you in advance.

I had an issue that my bootloader was an old version, I used the instructions here on "Update the bootloader"
Pi 4 Bootloader Configuration - Raspberry Pi Documentation

Now I can get libre to technically post, but not start.

I have tried downloading the latest 'start.elf' and 'fixup.dat' but it still will not start. (I tried it with both 'fixup4' and 'fixup4x' and the same for 'start.elf')

Update: LibreElec is displaying the splash screen, but all I see on the left is the following text endlessly repeating itself:

Starting Kodi Media Center...
[ OK ] Started Kodi Media Center.
[ OK ] Stopped Kodi Media Center.
Starting Kodi Media Center...
[ OK ] Started Kodi Media Center.
[ OK ] Stopped Kodi Media Center.

update: left running over night and its still repeating itself. (Starting and stopping Kodi media center)

Quote from Klojum

What is the date of your RPi4's firmware?

That's this right?

vcgencmd bootloader_version

If so, the date is: 'July 31 2020'

Also, I saw your comment immediately when you posted it, but this forum won't let me respond for 40 minutes, how are you to communicate with someone to fix an issue, if you can only respond every 40 minutes?