Well, I catched the error: Error Domain=com.google.ads Code=1 "Request Error: No ad to show.
Does it means i have to wait until Google sends ads for my app?
One of the apps i having this problem, is around a week ago its on the store...
That might mean that there are no suitable ads available in the region that the device asking for the ad is in. There could be a number of reasons for this, like no paying advertisers or your app doesn't fit the criteria that advertisers are looking for.
If you have other apps, one thing you could do is set up a house ad campaign so that whenever there's not a paid ad available you advertise your own app(s). That way you're not showing an empty banner in your app & you're making users aware of your other apps.