well, you should try to reinstall it.. Every WLM should turn on the notification automatically after installation. It might be the push function is OUT or something or pushfix is not functioning.

well.. try to search the "pushfix" over in the net... you might be able to find something there. Or else, try to reset the network and see whether it help.
There are many possibility of the push not working.. i got my pushfix malfunction which needed me to restore my iphone to get it work.. So check out whether the information over the internet will help to get you get rid of the problem.