unity ads isready(rewardedVideo) always false on android, help needed

hello, i'm getting a weird problem, when i have code and tested my ads manager it was working on editor and on my android device.

now i have upgrade to unity 5.5.0 and i'm testing some new behaviors on my game and it is working on the editor but not in my android device, in the editor i get the unity ads test screen that says that there will be an unity video ads and a button to let it close, but in my android device i don't get anything, i checked and isReady(rewardedVideo) is always...

unity ads isready(rewardedVideo) always false on android, help needed