Your gradle version is: 1.8
which is not working anymore so you probably have to update it:
1- Go to -> https://gradle.org/install check out the latest verion number.
2- In your project directory navigate to \gradle\wrapper\
directory and edit: gradle-wrapper.properties
file.
change:
https://services.gradle.org/distributions/gradle-1.8-all.zip
to:
https://services.gradle.org/distributions/gradle-3.3-all.zip
3- go to Tools→Android→Sync Project with Gradle files
4- If sync doesn’t do the job restart Android studio