This is because you never apply the doping to any atoms, so it's not active.
However, it anyway would not make much sense to use this charge doping method for a bulk structure, because all it really does it shift the Fermi level. It's a technique that can be used in an interface like a p-n junction to shift the Fermi level differently in two parts of the system, to mimic n or p doping. But in a bulk crystal, it will just rigidly shift the zero level reference, and the transmission remains the same.
It's a bit hard to see what the purpose of bulk transmission for an amorphous material would be, but perhaps you should just add an explicit dopant atom (and then I would look at the DOS, not transmission).
