Failed to load Interstitial Ad and thrown exception

Question

I want to plugin Windows Server SDK Interstitial Ad to my game. But it is alway throw an exception. I think that it is failed to load the ad from the server and thrown exception. I have add a event of OnAdError, but it is throw exception instead of call this event. I have show several screenshots. Why it is failed to load ad?  I am sure it able to connect to the Internet. Is it possible that alway failed to load ad from China? why it is not call OnAdError event when exception occured? Thank you!