Admob ads failed to load ad 3

Question

I have been trying to solve this problem but this is not working please help me out in this problem... ads were showing perfectly in my application but now they are not loading and returning error 3 on AdFailedToEvent event... searched google but i found the solution of mediation group i added that but that did not help me out Here is picture of my mediation group below

https://i.stack.imgur.com/tTf1Z.png

Answer 1

If you are using a debug build on your device, the chances of real ads being shown is very limited. Switch to a release build and real ads will start to show.

I have experienced this many times but after searching Internet for days, I figured it out on my own.