There are confirmed reports at Google AdWords Helpforums of a bug with the Google AdWords Ad Preview and Diagnosis tools.
Some are reporting that when testing the localization within the tool, the tool is showing that the ads are not running, when they are indeed running.
Dan S, an AdWords advertiser wrote:
I'm having a similar problem with the Ad Preview Tool but the ads themselves seem to still be running. Keyword Diagnosis gives same result as bubble and preview tool.
Google's Kathleen confirmed the issue and said the Google team is looking into it. Kathleen wrote:
Thanks for bringing this to our attention. This issue has been detected by our technical team and they are currently looking into this. I'll update this thread when I have more information!