never had the issue you are talking about here...
I still have the prototype black cone, and the new white ones comming tomorow. Maybe the white ones are a bit softer, but with the black ones I did not have any issue connecting my mouthpiece to it
let me see if I can show you...
When connecting the mouthpice, press against the buttom part of the cone, then press the mouthpiece in. There is definately a little 'nipple' on the cone that should fit into the mouthpiece.
and here it is with the top cap connected. Again easiest way to connect it is press the cone into the top cap, and while keeping it pressed insert the mouthpiece, and it should connect just fine...
this is what it should look like when you inserted the mouthpiece, and then slide the mouthpiece down into the top cap:
to use it you off course pull the mouthpiece all the way to the top of the closing cap.
hope this helps in any way, otherwise try uploading pictures so we can see what is the issue