Checkout this video tutorial from Javier Rollon.
The flaps sounds should be audibile only when the engine is not running. This is actually a feature. To get more informations about how to operate the flaps without hearing them, please read this post: http://www.simcoders.com/2015/10/18/all-you-want-to-know-about-reps-flaps-implementation/
In the last months many of you wrote an email to ask why with REP the flaps motor sound is not audible when the engine is on. That’s actually a feature. Le’ts see how you can use it to improve your pilot skills.