cortana can not hear my voice

Phone or PC????

On phone when you plug in it is probably thinking you have a headset with a talk button and condenser mic.

If PC it should not happen.

Can you provide more details? Device? OS version? Etc?

If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See this link for instructions on how to join Windows Central.