What device do you have?
What app are you trying to use when you get this message?
What have you tried?
When did you first notice this?
Do you see a green dot in your notification bar when this happens?
Have you tried to kill all apps running in the background and then tried again? Open your quick launch menu and close all apps then try.
Are you able to listen to audio in other apps? YouTube, FB, Insta, anywhere you can listen?