ipad imessage has pop up asking to sign in

My apad 2, which is about 4 yrs old, all of a sudden when I try to see my messages or send a text, the screen is light gray and a pop up says i need to sign into apple ID to activate my i Message.

Not sure why I would have to do this right out of the blue. so I signed into my account and nothing. It has been like this for 2 days now. I have rebooted the ipad several times, reset defaults to factory and still nothing.

I went into settings to see if switching on off button in messages would do anything, except I dont have that screen anymore. The screen that is there is the sign in page for apple so I sign in again and still nothing happens. The account has been verified. I still have email etc. Any ideas?