Than you for your follow up. The sequence of steps were:
1) Start drone and Drone Deploy app
2) Attempt to fly plan, failed after all checklist items are green
3) Power off drone, kill Drone Deploy app, make sure DJI Go wasn't running - which it wasn't.
4) Power on drone, start Drone Deploy, attempt to fly plan, failed
5) Power off drone again, kill Drone Deploy app, wait two minutes
6) Power on drone, start Drone Deploy, attempt to fly plan, failed
7) Kill Drone Deploy, Start DJI Go, Fly manually
8) Kill DJI Go, start Drone Deploy, attempt to fly plan, failed
9) Power off drone, kill Drone Deploy, wait one minute
10) Power on drone, start Drone Deploy, attempt to fly plan, failed
In all cases Drone Deploy failed even though all pre-flight checklist items were green.
At the time, I did not think to check the number of GPS satellites registered. On the way home I checked the Navigation system in my auto and it only saw five, sometimes six, satellites.
As mentioned in my original message, I suspect the overcast day was the root cause of the failure. However, it would have been helpful to either have a more complete diagnostic message or the option of turning on a debugging mode that would provide detailed information on the Apps progress.