Unity WebRequest never ends on android!

i’m using demo script from the unity manual about network post! when i yield return request.sendWebRequest() it keep stuck waiting to finish and never do. before de add of the sendWebRequest everything work just fine. someone can help me?

Which version of unity

I tried 2017.3.0p1, 2017.2.1p1, 2017.2.0p4, 2017.2.1p1! none of then i can’t make work on the API 17 of Android! testing on a samsung galaxy tab 10.3!

Can you show the code where you use UnityWebRequest?