Hi,
It should still be working.
As we've redone the whole checkout system, the code has changed, so something might have broken.
Also, we didn't test the new checkout with CB so it might still be a real problem.
The function that is being used in the "register" function in the file administrator/components/com_hikashop/classes/user.php
In there, near the end of the function, the function addAndConfirmUserInCB is called and that's this function which adds the user to CB.
So the first thing would be to add some logging in there ( with JLog for example:
docs.joomla.org/Using_JLog
) to see if that addAndConfirmUserInCB function is being called.