What version do you have, im going to assume the cd version, after installing make sure you download and install the update from
here for your correct language.
After that run the update in game and you should be good.
Also if your installing jotr and esc, install them first and then run the update from above, then the in game update and you should be right.
Alternatively if you have combine arms, you can also uninstall and then re-install using the installer from
here, its the later combine arms installer.
Finally if your running windows 7 or higher, you may want to adjust the icon it uses to launch the game so it runs as administrator, you dont have to but you will find that you dont get any ping response times for any of the servers unless you do, although the game will still run perfectly fine. To adjust it, see step 2
here, the same thing is required for win8 or win10, the options will be the same.
:)