Okay, fist of all you have to play the 707 in FS 2004. It currently doesn't work with anything else.

Second, Make sure that you have set off the Failures. Go to FS Menu, click Failures and make sure everything does not have a tick.

Third, do what dewang_ is recommending.

forth, If that does not work then during flight click ' and use the numbers. That will automatically tune your radio and equipment.

Happy flying!