I have and unlocked iPhone for with T-Mobile USA which i update it to 4.2.1 successfully without upgrading the baseband, but now i wont receive any notifications, not from the facebook app, im+ pro app, liveprofile app, i dont get any notifications from any of the apps and i have Push Notifications on on my settings and for all the apps. Can anyone tell me how to fix this plis???

How did you activate after restoring? Activating with an AT&T SIM is the ideal solution, but if you hacktivated you should take a look at SAM Subscriber Artificial Module

I did hacktivate, so, if the sam solution doesnt work ill just do th restore again without the hacktivation since i have a couple of att sims

Hacktivation doesn't include any client side certificates for push notification. SAM or AT&T SIMs should work. Be sure to avoid restoring from iTunes backup as that can sometimes restore incorrect data related to push notifications.

ok, so, i tried the SAM, i installed it, went to settings -> SAM, Deactive iPhone, then went in again and pressed revert lockdown to stock, connected to itunes and the iphone still appears as activated, never asked me to activate the phone, am i doing it wrong? If anyone can help me please

Don't you have an option to use the T-Mobile Carrier Bundle or something like that? Sorry I don't know much about SAM, I always activate with the AT&T SIM card.

when u go in the auto detect option, there's 3 more options: by bundle name, by country and carrier and manual

T-mobile (USA) should be supported by the auto detect mode in SAM. The autodetect could go "wrong" if you have installed some Cydia package that adds a T-mobile bundle with carrier settings. These may break the autodetect (I'm guessing here but it's a plausible theory). In that case, you may have more success to choose "by bundle name"

It didn't work. I pressed revert lockdown, connected the phone to itunes, got the invalid sim message, to enter a valid sim(att) on the phone, i switched the sim, while connected to itunes, nothing happened, disconnected the phone from itunes, pressed de-activate iPhone and connected to itunes again and the phone was already setup as my iPhone as i had before, didnt go through the activation windows/proccess

Search for push notification certificates regeneration, there is a free cydia package that you can install and it will generate new ones for you..., did this with a friends iphone and worked, had to install the package more than once till it generated good certificates but it worked perfectly.

Here is the text from another post:
goto cydia, add source Welcome to NERV Repository (cmdshft . ipwn. me/apt/)
and install push doctor !!!
Read here: FREE Unique Push Certificate in Cydia