Can you enter the camera view?
Can you start the motors?
It might be just a loose of video link

Have you tries a different device or different USB cable?

This happened when I did the latest firmware upgrade, even though my dji go app Was already updated as well no matter what I did rebooting the iPad and the aircraft nothing in cam view... Not only that but the app crashed every time going back to the iPad's home screen, never seen this one before after one year of ownership.. Then I deleted the app completely from my iPad and then reinstalled it from the App Store and everything was good to go after resetting a few of my preferred stick curves and RTH safety settings etc....