Check all the dependencies, whether they are valid or not.
Or for a temporary fix, try offline mode.
To enable this setting go to:
Preferences -> Gradle
In the right side options go down to "Global Gradle Settings" and check the "Offline work" box.
- Build from the command line to know the exact source of the problem
In windows
gradlew.bat assembleDebug
In linux
chmod +x gradlew
./gradlew assembleDebug
- If nothing works, You can also try to delete all contents of folder C:\Users<Username>.gradle