<<ISSUE>> -- Failed to load AppCompat ActionBar with unknown error. Tip: Try to refresh the layout. -- <<Solution>> 1. Navigate to build.gradle(Module: app) in the project explorer on the left hand side. 2. Change as below in dependencies section implementation 'com.android.support:appcompat-v7:28.0.0- alpha3 ' => implementation 'com.android.support:appcompat-v7:28.0.0- alpha1 ' 3. Click 'Sync Now' on the top right corner