Plugin with id 'com.google.gms.google-services' not found

Question

I have followed this link to integrate ads in my app. But it shows this error:

This is

Answer 1

Had the same problem.

adding this to my dependency didn't solve

classpath 'com.google.gms:google-services:3.0.0'

Adding this solved for me

classpath 'com.google.gms:google-services:+'

to the root build.gradle.