Other than the reeds that are not sounding, do you notice a significant difference in sound compared with the old reeds?
It is interesting that in comparing multiple air chambers, I have not seen one yet that does not route the air to the high notes first. They are also very shallow. Hard to tell from the pictures, but your adapter appears quite deep, which would significantly increase the volume of the air chamber. Higher volume, slower movement of air with a given input. Maybe not enough to activate the reeds. In other words, I think I agree with Brendan, although I have no idea what the dreaded Helmholtz Resonance Coupling issue is. I wouldn’t think the volume would be anywhere near what would be necessary to generate Helmholtz resonance. 8^)