Did you get a message from someone asking for your email and when you try to write back, it says that they are not a valid user? If so, it's a SCAM, and etsy has already deleted their account.
Or, have your messages been muted?
@Jeaquelare: Are you using an Etsy app or a browser? In what way are you unable to send a message? Are you getting an error message? If yes, what is it?