The most common reason you would get no sound from your microphone is that you do not have the "Source Select" drop down menu set to Mic 1.

This is located in the upper left hand corner of Gearbox (middle of the POD Farm application window, to the right of the "MUTE" button).

If you own a TonePort UX1 and have selected Mic 1 and you still get no sound, your microphone may require Phantom Power. UX1's do not provide Phantom Power to the XLR port. Only UX2's, KB37's and UX8's have this feature.