Unity iOS BackgroundFetch Example only return null

I've been following the code sample below from Unity to get try out background fetching on iOS. However, I can't even get the example to work properly. I followed all the instructions and read the associated documentations, no clue. Does anyone have any luck with it?

Link: https://bitbucket.org/Unity-Technol...n/BackgroundTasks/BackgroundFetch/?at=5.0-dev