I tried the bell with Riley. It freaked him out and he wouldn't go near it.
A spotbot was my best friend. Right when I thought he would never get it, he just started going outside all the time. It was the same with Kaleb.
Urgh that sucks! the bell was the only thing that worked for me. My mother house trained all her dog by attaching them to her, and taking them out every 15 minutes.