Chasing a Moving Target
DJI does a great job of adding new features and addressing issues as they arise while adding support for new hardware. The problem with that is for developers writing an app that supports various devices and versions of firmware, it can be a bit of a moving target.
It can take a while for the aircraft to connect so give it a couple minutes. If it takes longer than that there is likely a problem. The top status bar in Map Pilot will say "Connected" when the app has connected to the remote and recognized that there is an aircraft present. Users are presented with a popup when the connection occurs. Getting the red triangle that denotes the aircraft location depends on the aircraft's ability to get a GPS lock. If the aircraft is inside this my not be possible so keep an eye on the number of connected satellites.
These problems are frequently caused by the PAF (PSA on Phantom 4) switch not being in the F (P for Phantom 4) position when the app is launched. It is also likely that the DJI Go app is running in the background and attempting to connect as well. Be sure to fully close the DJI Go app by double clicking the home button to bring up the currently open apps and swipe up on the DJI Go app.
Sometimes the DJI Go app will have a pretty good hold on the connection so unplugging the cable and closing both apps will sometimes be required. Restarting the iOS device can often help as well.
The case with the camera not taking images is an especially troubling one since you can waste a whole lot of battery without noticing that anything is wrong. Make sure that the camera preview window is blinking as it takes the still images and that the grey circles are being dropped along the flight path as the aircraft executes the mission. When the non-imaging condition occurs, we have found that an aircraft and remote power cycle is needed to recover.