I had the same problem and contacted the Leave It On customer support. There is something in the OS that is blocking leave it on to show pop-ups for emails. It works for bbm, txts, Facebook, etc though.
I think there is a way to get it to work, but you have to re-install the OS and delete some file. Personally not worth it to me to mess with that so I'm just waiting for an update with a fix or a new OS that doesn't won't cause the problem.
