AdMob Ad is not showing

Question

I am getting ad in the test device only. Other devices showing the following error :

W/Ads: Not retrying to fetch app settings
I/Ads: Ad failed to load : 3

Documentation says this error means :

The ad request was successful, but no ad was returned due to lack of ad inventory.

The AdUnit is not new, waited for a few days, but still getting this error. The App is not published in play store yet. Whats wrong here?

Answer 1

having the same problem. there are hundreds of people having the same problem. it started happening on 11/27/18 my last ad impression was on the 26th