It basically means you're on system menu 4.3, and bannerbomb no longer works for that version of the sys menu. You'll have to use a different exploit for your homebrew endeavours. There are currently 3 other exploits you can use: Smash Stack (requires US version of SSBB), Indianapwns (requires any region Lego Indiana Jones game), Yu-Gi-Owned! (if you're 4.3E) or Yu-Gi-Vah (if you're any other region... these last two require Yu-Gi-Oh! 5Ds Wheelie Breakers).
You can search for said exploits and instructions at wiibrew.org
Good luck!