Hi guys. I bought a Phantom 3 Professional in June 2015. It works properly untill this week. The Drone and the Controller are connecting but when i connect the iphone to the controller nothing happens. The ios iphone can't connect to controller. I'm using an Ipad and a Iphone 6s to connect and both has the same problem. My controller is a "300A" My Phantom is a W323.
Yesterday the DJI Support on Facebook helped me to try every possible tests with the controller and the aircraft with smart. We tried different cables, differente devices (IOS and Android) and a lot of ways to connect it closing app wih/without cable and start app again, App open and just connecting the cable.

The videos:

Please confirm your App version and RC firmware version are up to date . And try to reinstall the DJI Go App . If all that don't work , please check if there's any problem to the USB port of the RC .

This sounds silly, but on the How to Connect screen, try swiping left to the Matrice 100 or right to the Inspire and then BACK to the Phantom and see if the Camera button highlights..

Also, in the first video, you have the antennas crossed. Your P3 antennas are oriented vertically in the P3 legs. The antennas should always be parallel with the legs. The second video is better for antenna orientation