Call of Duty Black Ops II will not play online

SOURCE: Playing Call of Duty 4 Online - PS3

if you are using a wireless connection the signal may be to weak. if not you can try deleting your game and save data. you will lose any single player saves you will also have to re download any map packs you purchased. the game should also do an update when you load again after deleting the game and save.

SOURCE: Lost my key code to Call of Duty 4 - Modern Warfare

finding your Key Code For COD4
running Windows operating systems and playing COD4 to find your CD Key.
Click on “Start” then “Run”
In the “Open” field enter “Regedit” and click on “OK”
Windows Registry Editor will open.
Expand in this order: “My Computer”, “HKEY_LOCAL_MACHINE”, “SOFTWARE”, “Activision”, and finally select “Call of Duty 4′
on the right side you will see “codkey”.

SOURCE: PS3 Call of Duty 4 Modern Warfare 2

I have had the same problem in the past all i did was sign myself out of the ps3 and signed in again, if that didnt work i dissconnected myself from the internet and connected back

SOURCE: My Xbox 360 freezes when I try to play call of

make shure your game is not messed up

SOURCE: My Modern Warfare 2 Game Wont Let Me Play... Please Help!!!

It could be your router or network settings for your internet. Do you use Port forwarding? The Playstation site tells you all the ports you need to use. Also try putting your playstation in a DMZ.