I dont have a carezza, but it has similarities to the classic, so will try to help out, maybe others will offer more advice.
Does the pump work when you hit the brew switch (you will be able to hear it)? If so, does any water go back into the tank? Try all tests without the group handle in place so you can see if any water at all comes out the shower screen. Let us know how it goes and well try to work out what it might be.