Could either be just a Chat Ban (so can still play, unlike a full Ban).Or just a Lag in refreshing/sync'ing the Chat pane with your device (your device doesn’t get a response from server that your msg had been received, even though it did).If that’s the case, Exit and restart game, and your message should be there (especially if into Alliance/AQ/AW chat, since global might have scrolled past there by then).
Please contact support using the in-game link for account related questions.