I have followed many answers about that error here, but my problem is not solved. Every time I run my app no ads appear and I get this error message in Logcat:
Solution:
How to setup payment methods in AdMob:
If you are still experiencing problems, feel free to contact me via email: ashkaushik0007@gmail.com
i found the error from the emulator after i install the app on real device the ads shown perfectly thanks everyone and i hope my answer being useful for others ..
One more reason can be: Missing payment information
Your ad units aren't serving ads because your payment information is missing. Add your payment information now. Learn More
Make sure your ads not violate Google Ads rule, otherwise you have to fill appeal form first to contact AdMob support and after they re-enable your ads serving, ads should appear.
I added the code below for the testing environment
AdRequest adRequest = new AdRequest.Builder().addTestDevice(your device id)
//When you testing on emulator
.addTestDevice(AdRequest.DEVICE_ID_EMULATOR).build();
If you are using live admob ads id in development mode application , it will show this error.
Use debug mode admob ads id during development and live admob ids in release mode app