You can inspect your CSV log files in the DJI Diagnostic column to see what the problem might be. There could be various hardware issues stopping the automated flight.
If that isn't the problem and it is sunny it is most likely the collision avoidance system. You can either turn that off in the DJI app or make sure the optics are all super clean. If they are smudged and get the sun on them it can do all sorts of weird stuff. That will likely show up in the log file too.