Gradle Sync Failed Android Studio 3.6

Ran into the same issue and deleting ".idea" folder inside project directory and deleting ".gradle" directory from home helped me resolve the issue.

Run to the very same error a while ago. This worked for me.

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

Source: Cannot enable Gradle's offline mode on Android Studio 3.6