Independent Apple Watch app trying to access WIFI without iPhone

I developed an independent Apple Watch that can access network resources on its own using NSURLSession without going through the iPhone. This works fine if the iPhone is on, but if I turn the iPhone off it is not able to connect. Why does my app lose network connectivity when the iPhone is off even though it's a standalone app and the Watch is connected to my WIFI? Is there anything special I need to do to get this working? It appears that no apps work with the internet when the iPhone is off. WIFI is enabled and connected to my WIFI network under the Settings on the watch