Push Notifications usually don't work good on hactivated iPhones (2G,3G,3GS). Many fixes have been shared before regarding this, most recent fix was "PushFix" via iPhoneil available in Cydia, but it wasn't a proper solution and it stopped working after a while as it used a single certificate for many users causing wrong push notifications and battery drainage issues. Now Ver.2 of PushFix is available, and it actually works very well, basically the error/issue which has been rectified in new release is that you get a unique certificate for your hactivated iPhone against your mobile EMEI (International Mobile Equipment Identity), each unique certificate costs US $5.99.
Please follow following steps to enable Push Notifications on your hactivated / jailbroken iPhone (2G,3G,3GS) running on firmware 3.1.2. Please keep in mind that you need a fully Jailbroked and Unlocked iPhones to use this application. If you already have an unlocked iPhone, please proceed with below instructions to install PushFix 2.0 App.
Step-1: You'll need to purchase the certificate first by providing your EMEI, and US $5.99 off course :)
Step-2: Once you are done with purchasing, simply install "PushFix 2.0" via http://cydia.pushfix.info as shown in snapshot below, if you install the application without purchasing the certificate, installation will fail as it checks your IMEI on server before installing the package.
UPDATE: Push Doctor App is available now to enable / fix Push Notifications on Hacktivated iPhone 3.1.3 for FREE!Contact Us for News Tips, Corrections and Feedback