Whats going on with facebook messenger? My messages arent sending?

Yesterday as i was texting with someone i sent the message but it didnt deliver. It just said sent with the white checkmark but not delivered with the blue checkmark. Didnt think much of it so i didnt send another one and i fell asleep. Today i woke up and it still hasnt delivered. I sent another one and that one hasnt delivered either. It says the person is active but they're not getting the message? Whats going on?