Well, I get this message all the time using AdWhirl:
Unable to fill ad request. This is a common situation.
I think it's from the AdMob network. I also have a couple of other networks (registered yesterday) and I never seem to be getting any ad requests filled. In test mode it does work though. Now is this common and will it pick up?
Turns out it went away after a couple of days. I guess AbMob had to review the application first.
Not only is this normal when the app is new, but it is also more frequent depending on your geographic location. In Switzerland I had ads all the time. While I am here in Brazil now I face much more often the "no inventory" issue.
In any case you can't do much about it, other than to rollover to another fallback network if you use Adwhirl or a similar solution.
