unity ads not ready on test mode

I am using unity ads on test mode for many days and it was working fine, suddenly ads stopped to be ready on test mode
and I tried with different projects on my dashboard (unity ads page) and nothing happened, I spent my whole day trying to find whats wrong and I have no explanation.

this worked for me.

try this in awake() :

if (!Advertisement.isInitialized)
      Advertisement.Initialize(GameID, testMode);  //// 1st parameter is String and 2nd is boolean

it supposed to be auto initialized if you are using Services window, I contacted support about this issue, and this was the answer " There might have some problem in the ads initialize earlier. We did solved it in newer version of Unity. You can always add a If clause to manually initialize the advertisement. " .

good luck.