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 IL-2 Sturmovik, make sure everything installed correctly.
Exit Steam entirely.
Browse to your IL-2 Sturmovik installation folder (Usually C:\Program Files\Steam\steamapps\common\il-2 sturmovik cliffs of dover\)
Run the following installers:
Reboot your computer and test the issue again.