Here's the problem with The Family Man; Brett Ratner isn't a great storyteller. The guy was largely in the music video business when he was asked to take on this movie. The script wasn't great either, it was a poor man's It's A Wonderful Life (even going so far as to borrow the whole bell idea as an audible cue). So, you need to take it with a grain of salt that Cash doesn't appear when Jack first rings the bell. In fact, Don Cheedle was grossly under-utilized in the movie, which I see as a huge failure on Ratner's part.
At either rate, the bell does finally get rung by Jack's daughter when he teaches her how to ride a bike. At this point, Jack has fallen in love with his "what could have been" life, and the bell sound signifies that he's going to have to go back. And he knows it, which is why he immediately looks disappointed after hearing it.