1. If you have the demo installed, uninstall it and run a search to find all file associated with the demo, delete those as well.

2. Update windows (probably irrelevant but i realized i had not done that in a while)

3. Reset the firewall exception (again probably irrelevant just one of the many things i was trying at the same time)

4. Open EA download manager, will most likely prompt you to log in/update. (Do it)

5. Mine opened to a screen saying no games detected, clicked on the settings button (looks like a gear/cog) in the top right corner, went to redeem game code.

6. Entered my Crysis 2 CD key (not the limited edition key). It added the game under my account

7. Open Crysis 2 (If firewall exception reset alt+tab and allow it to access networks again)

8. Logged in fine for me after this point

**** I understand this by no means is a definite fix, i just know it worked for me so hopefully it can do the same for some others suffering from the same issue ****

Cheers!