Yea I think you need to provide WAY more information than that, & then people will try help. 
- Is it the flybywire or default?
- If so, have you tried removing it and reinstalling it? (try another version like the developer version)
- Are you using a peripheral (Joystick, Yoke etc) or does it not even work with mouse clicks?
- Since what upgrade? SU5? Loads of people are having issues with peripherals so have you checked your keybindings?
- Have you done the usual thing of removing everything from your community folder to reduce the chance of conflicts.
I could go on & on!