Hi,
There are a few things to be aware of that I've found:
1) Android charges the phone off the controller so it consumes the battery faster (iPhone doesn't)
2) The S8 has a soft 'home' control which just so happens to be under (or right next to) the Take off button in the DJI Fly app which can...
I just had the same issue and resolved it as mentioned above by putting it back in the drone, powering on and waiting a minute. I did also do a small quick recording (which was also mentioned as a fix, but not sure if it was just the timing).