My iMessage is not working

you need to toggle imessege in 'messages' settings

and to choose your phone number in send new message on 'send & receive'

on 'text message forwarding' toggle your ipad/mac if you wish

make sure you are connected to internet, since imessage works only over the net

something more basic - does the recipient use iMessage and in a network location?

make sure you've checked 'start a new conversation from' in 'send & receive'