The community is also a great place to check out. Try these places for help from other users:
Please review the Third-Party Game Support topic to determine whether your question should be directed to the game developer or to Steam Support. Sending a support request to the wrong party may result in a delay in processing your request.
If you're encountering issues with launching Fallout: New Vegas, make sure everything installed correctly.
Exit Steam entirely.
Browse to your Fallout: new Vegas installation folder (Usually C:\Program Files\Steam\steamapps\common\fallout new vegas\)
Run the following installers:
Reboot your computer and test the issue again. If the issue persists, contact Fallout New Vegas support
To activate downloadable content for Fallout: New Vegas, double-click on the game's entry in your Library list.
This will bring up the game's launcher menu. Select the "Data Files" option.
From here, you can select the content you would like to have available in the game.
To view the additional content subscriptions for Fallout that are registered to your account, please do the following:
Alternatively, you can also find the DLC (downloadable content) for a game by right-clicking on the game, selecting 'Properties' and navigating to the DLC tab.
DLC for this title will be presented in the form of quests to visit a new location. If you are having trouble accessing or locating these quests, contact Fallout New Vegas support for detailed instructions.