My App was working fine, then i add com.splunk:mint-android-sdk, which required upper version of gradle, so i upgrade the gradle to from 2.1 to 3.3. after that i am facing i
Please follow these steps :
Open Your project.
Go to the Left side of the Gradle button.
Click button above image show .
if this type of view you are not in offline mode.
Go to Build and rebucild the project.
The above worked for me.