That blows. I assume the 5D3 is one of those Canon bodies I'll try the "manual hack" method to see if I can get the Bees to sync up.
I'm not sure about the 5D3, but the 1Dx certainly doesn't work with the Phottix. Since they both came out around the same time with similar design features, I would guess its possible. If that is what you are using that would seem to confirm it.
Phottix keeps hinting that they are coming out with new features for everyone with their next firmware update, but as I've told them, just get the current body Canon cameras to work. Add extra features later AFTER your lineup is functional.
I would really like to see this system work, but so far it is nothing but money ill spent.