How do I enable iMessage using my phone number on iPad?

I use to be able to send receive messages with my Ipad using my phone number instead of my email.i just updated the ipad to current iOS and \Now the phone number isn't even listed anymore. Everything on my seems Iphone seems fine. All my id's are listed on that device. I have done a hard reset on both devices and signed out and back in on both devices. When I go into setting-imessage-send receive. I only have 1 email listed. Any suggestions on what else to do? I have seen other discussions on this subjet. Many talk about caller Id but I don't see that in my options.

i messages is on on the ipad but on the iPhone it keeps shutting off.

Any help is appreciated thank you

[Re-Titled by Moderator]

Original Title: iMessage not working