When you speak into the mic does the AF
meter bounce? If it does, then your problem isn't the mic, but from the audio output of the receiver to
system. If it doesn't
bounce, like William said, make sure that the transmitter's frequency is the same as the receiver frequency.
If the frequencies are the same, make sure that there is nothing else using that frequency that might be
blocking out your mic. If there is nothing else on that frequency, set a different receiver to the mic's transmitting frequency and see if that works.
Perhaps, it is locked into
mute? I've done that a couple of time to keep
ENG crews from getting too close to my frequencies.
Good Luck.