Multiple Controller Installation

I have a Two (2) Gen 2 installation with a Master Valve. This installation also includes 2 Isolaters. I followed the instructions provided on the Rachio Tech Support pages. I also have an Ambient Weather WS2902 Weather Station as part of the overall installation. I am using data from the weather station for Weather Intelligence. Basically, everything appears to be working OK. According to the Multiple Controller installation instructions, I should be able to run a zone from the Left Controller at the same time as a zone from the Right Controller. In reality, that is not what is happening. When you look at all the indicators (lights on the controller and the countdown clock in the app), it appears as though this is happending. However, only water is coming out of the sprinkler heads for the controller that was started first (during my manual tests). Any ideas? Not really sure what question to ask. I would like to try to run both controllers in parallel since I have a somewhat large lot with lots of zones and would like to have everything finished by 7:00 AM (right now starting Left at Midnight and Right around 4:00 AM). I am in North Texas (DFW area) with rather significant watering restrictions (days of week and time of day). I realize the pressure and water volume might be reduced.