there are few thing you can try to resolve the issues.
1. reset your router and modem or gateway.
2. goto the web browser and delete cookies and hitory.
3. double check your router setting and make sure your router is configured correctly(port forwarding or dmz ect)
4. hold the on/off button til it turn on then beeps then turns off again. then hold the on/off button again till it beeps twice.
5. do a filesystem restore.
6. repeat step 3 and do a restore database(warning this step you may loss you old pns chat history)
7. uninstall crysis 3 game date (NOT saved game data) then reinstall game and redownload the DLC from your downlaod history. (as long as you do not delete saved game you won't loss any of your save points, ect).
any one of these steps may help you so its not necessary to have to do all of them. just do 1 at a time and try playing. if it doesn't help try the next one. good luck, PM me if you need more help.