always buffering if play simple chinese ads

Dear Unity,

When I test unity ads SDK on my iphone5s device it will show as buffering all the time, but in the same network environment if I run the app on simulator the ads will be played very smoothly. As I saw, on real device it trying to play a Simple Chinese ads but on simulator it played an English ads.

In my point of view, maybe the ads played base on the location (I locate in china) and download the ads resource from different server, but it really doesn't make scene to me that when I play another iOS game with unity ads which show ads with any problems.

looking forward for you reply and helps.

Many Thanks.