Hi Stefan,
Did you selected the appropriate drone in the drop down list when you are in the map view of the app? For the Phantom 3 Pro you should select P3P.
Make sure also that you are using the beta version 2.0.4 with the firmware version V1.4.0010 installed on the drone.
With the Phantom 3 you do not need WiFi to connect to the drone, you should use a USB cable between the phone and the remote controller.
You can find more information on how to use the beta on the following page:
Note that the Phantom 3 is not yet supported on iOS but we are working on that. We will post updates on the following page when we have a beta ready:
https://community.pix4d.com/t/4464
Best regards,