You can't use the resource cheats in campaign mode. If you wanna cheat to survive and enjoy campaign mode (like I do), if you have the latest version of Dawn of War...uninstall it then reinstall. DON'T download ANY patches, start the game, then use the trainers located on this page.
What sucks is if you ever want to online play, like I do to comp-stomp with my bro, you will have to patch...then the trainers won't work. They only work with the latest version. Since we don't play online too much, I just patch...play a few hours online...then when I'm done, uninstall and reinstall again so the trainers work. Though, I make damned sure to save my Profile so I don't lose my saved games or custom painted armies.