Can't fill tank, usual fixes didn't work!

The thing is, in my understanding there might not be very much vapor needing to exit there: scarcely any from inside the bladder (because it's a bladder, and conforms to the liquid fuel) and a bit more from the small secondary tank where the fuel pump and level sender live, and the normal path for those is through the canister, then through the space between tank and bladder, finally exiting through the fresh air valve (along with the non-vapor-laden air being displaced from that space as the bladder expands.

But then if past overfilling has left the charcoal canister all muddy, or the fuel cutoff valve liquid-filled, I guess I could see that path being restricted.