Gradle Sync Failed Could not GET 'https://dl.google.com/dl/android/maven2/com/android/tools/build/gradle/3.1.3/gradle-3.1.3.pom'

I found the solution.

• The problem was I set proxy details of my University proxy server for internet access in Android Studio. When this problem appeared I tried build the project with proxy on internet connection with proxy but it did not work.
• Then I removed the proxy from Android Studio preferences and connected to non-proxy internet connection but the problem did not disappear.
• Then I Googled a lot and came here but could not find the root cause.
• I updated AS from 3.1.3 to 3.2 but the problem still persisted.
• Finally, I started looking for hidden proxy server details in AS and found them in gradle.properties file located Gradle -> Resource Bundle 'gradle' -> gradle.properties.
• Deleted the proxy server details in this file and ran the build with successful completion after performing some packages update on the suggestions Android Studio.

Bingo!