I pulled the rotating adapter off my ProS and noticed that at the lower right corner (when facing the back of the camera) my rotating adapter has a floating pin (that I think engages the pin that you referred to on your camera that sticks out when the camera works).
On the handle of the dark slide, there are two pieces of metal that wrap around the handle and engage a tiny lever mechanism. If I push the dark slide in, the metal on the dark slide pushed the tiny lever in and the floating pin will not push in. When I pull the dark slide out slightly, the tiny lever mechanism is spring loaded and follows the metal piece on the dark slide out, allowing the pin to push into the rotating adapter. I think the spring loaded tiny mechanism on your rotating adapter is not moving out of the way of the floating pin, which in turn is not allowing the camera to fire.