I created a new Ad unit ID around 4 hours ago and started using it in the release build of my unreleased Android app. But all I get is a blank view and the following logcat output:
W/Ads: Received error HTTP response code: 400
W/Ads: There was a problem getting an ad response. ErrorCode: 0
W/Ads: Failed to load ad: 0
I don't know the exact time it took but 12 hours after creating the new Ad unit ID it was active.