From what i have read its something about your phone not having the ability to use either 2.4 or 5.8ghz for wifi ( not sure which one) the drone uses one or the other to make the connection hence it doesnt work
From what i know, you have to select one person, but then if multiple people are in frame the tracking gets confused and quits, i saw a guy try a Rocket with multiple people and as it flew back it went askew and crashed
After a chat with DJI support they have requested i send it in for repair, its still under warranty so hopefully they can sort it for free. i'll update this thread once i know more