"Activation Required" Problem On iPad Air 2

I Have A Really Annoying Problem on my new iPad Air 2

That Is : The iPad askes For Activation Probly Every 30 Minuties

And It Says "Activation Required " And I Don't Know What To Do

IS This A single Problem And If It's a single problem Then How

To Cure It

And If It is a popular Problem Then What is The Solution

And I am Working With (ios 8.4) and even before the update the

Same Things Used To Happen

Please Somebody Help Me And .

Thanks ..... Dr.Heba Hossam