Have had some problems accessing the server with steam versions 2.1, 1.8 and 1.7
Not sure what the exact problem was but I did the following steps and it worked.
To Reinstall game to 1.7 version
1) take a picture of your Key code (Options/Multiplayer/Keycode)
2) copy to an accessible folder as backup the current game folder ( c:/Program Files (x86)/Steam/steamapps/common/ Call of Duty 4 )
3) Open steam and uninstall game ( right click game / Manage / uninstall )
4) Open folder (not backup) (step 2) and delete the hole folder.
5) Restart computer
6) go to steam and re install game
7) go to game folder (not backup) and copy the iw3mp.exe to your backup folder and place it with a reference version 1.8 (steam will download that version)
8) download 1.7 version iw3mp.exe from Pear's post
https://fhclan.com/forum/index.php?topic=4155.159) delete the iw3mp.exe from your game folder and replace it with Pear's post one.
10) delete servercache.dat file from your game folder
11) go to your backup folder and copy servercache.dat to your gaming folder.
12) go to your backup folder and copy "players/profiles/"your folder") to the same place in your gaming folder
13) I only launch game from the iw3mp.exe file not from steam. u can do a shortcut of that file to desktop
All done you should have your profiles and rank as before. If you lost rank go to net jam server and type
$rankup
$unlockattachments
Hope it helps. all this mess happened when I tried to upgrade to 2.1 version (many servers require it now)
Cappy