After updating iOs 11.1.2 to iPhone6s Plus and iPad Air then
Now I can not open DJI Go Creat. This is why I can not fly Inspire1 V2.0, Phantom 3 Avance and cannot access to  Osmo Plus and Osmo mobile
But the DJI4 app is still available for Phantom4.
Can someone suggest a solution?

Hi there, this is a known issue in IOS 11.1.2 and has been fixed in IOS 11.2. I'd suggest to update to the latest OS and reinstall the APP to check whether the issue remains.