I dont know why your mic doesn't work but a friend of mine managed to get chocolate in the microphone hole from being in her purse, I dug it out with a pin and now all is well
Hi. I've just started having the same problem. Like you, putting it on speaker works fine, otherwise those on the other end can BARELY hear me, but I hear them fine.
Since the speakerphone works, I think that rules out the microphone.