Mic doesn't work on all 3 FL

[Lowamc]

There should be no specific reason your microphone works on other server besides FL.
As brute said, go to "controlpanel>sound>recording", and ensure that your microphone is set to default.
Go back ingame, and try it out in the voice option area in the options menu. How does it sound? If you hear your voice it works. If it does not work ingame, you probably are not holding the correct button.
Go into "Options>Keyboard" and look for the voice chat button. Make it a button of your choice. Retest it ingame.
Still doesn't work? go back to keyboard options and hit "default buttons" (or something of the sort.) The default should be X.

Let us know how that works.

That didn't work, sorry.