I\'m using the new Android Studio 3.6 Canary 9 to test new functionalities, and I cannot enable Gradle\'s offline mode.
In Android Studio P
From the Android Studio 3.6 new features blog post:
New location to toggle Gradle's offline mode To enable or disable Gradle's offline mode, first select View > Tool Windows > Gradle from the menu bar. Then, near the top of the Gradle window, click Toggle Offline Mode Gradle offline button in the Gradle panel..
Here is the link -- hope that helps!