Could not resolve com.google.android.gms:play-services-ads

I am using the artifact play-services-ads but it cannot be resolved.
As the website of https://developers.google.com/android/guides/releases demonstrates, the artifact of play-services-ads has been released on https://maven.google.com repository. However, I added repository google() at file build.gradle, it still cannot be resolved and the error message is as follow:

Could not resolve all dependencies for configuration ‘:app:_debugApkCopy’.
Could not resolve com.google.android.gms:play-services-ads:11.0.4.
Required by:
project :app
Could not resolve com.google.android.gms:play-services-ads:11.0.4.
Could not get resource ‘https://maven.google.com/com/google/android/gms/play-services-ads/11.0.4/play-services-ads-11.0.4.pom’.
Could not GET ‘https://maven.google.com/com/google/android/gms/play-services-ads/11.0.4/play-services-ads-11.0.4.pom’.
Connect to 192.168.100.6:8080 [/192.168.100.6] failed: Connection timed out (Connection timed out)
Could not resolve com.google.android.gms:play-services-ads:11.0.4.
Could not get resource ‘https://jcenter.bintray.com/com/google/android/gms/play-services-ads/11.0.4/play-services-ads-11.0.4.pom’.
Could not GET ‘https://jcenter.bintray.com/com/google/android/gms/play-services-ads/11.0.4/play-services-ads-11.0.4.pom’.
Connect to 192.168.100.6:8080 [/192.168.100.6] failed: Connection timed out (Connection timed out)

Do you have any suggestions?