Difference running app on apple watch and simulator

I see a difference when running my app on apple watch (hardware) vs simulator.

My swift 2.0 program (which calls helper method to parse a JSON file and then displays content in interface Controller) runs perfectly well on Xcode simulator.

When running on watch, the data is not displayed.

Debugging on watch most of the time does show that the response from the helper (delegate call) is not received.

Any idea how I could trace the issue ? Any similar problems?