"upgraded" to IOS 11.4 all messages disappeared, and I can not send or receive new ones

Since upgrading to the new IOS, my messages screen is blank, and I can not send or receive messages. It still works on my Mac, and iPad 2, but my $1000 iPhone X can not send a text. 

:I had this exact same problem with my son's iPhone SE. Right after the iOS 11.4 update the Messages app stopped working. You could start the app, and try to compose a text message, but the send arrow button didn't work. Also, none of the previous or new messages were visible on the screen. The badge icon showed the numbers of unread messages (and the app was apparently receiving them), but you couldn't read them.

I chatted with Apple support twice and the only recommendation was to do a Factory Reset on the iPhone and restore from a backup file. Did this twice, but the problem persisted. The Apple senior advisor stated the problem was probably something in the backup file conflicting with the new OS. The implied final response was to do the Factory Reset an reload all apps from scratch and not do the restore from a backup file. This wasn't an option, because my son would have lost all the data files associated with is apps.

How I fixed this issue:

This is what I did to fix the problem. I went into the "Settings -> Messages" and turned off everything option. I turned off iMessages, SMS, MMS, etc. I also switched "Saved Messages" from "forever" to "30 days" (which then asked if it could delete old messages and I said "yes"). I then turned all these options back on, including "iMessages". Once I did that, everything worked again! I can see his new text messages, receive new ones, send out messages. Everything was good.

So, I think there must have been something with the old stored messages that caused the problem. Hope this helps others with the same problem.