I also faced the same problem and the problem was that the libraries were missing in some of the following files.
settings.gradle, app/build.gradle, package.json, MainApplication.java
Suppose the library is react-native-vector-icons then it should be mentioned in following files;
compile project(':react-native-vector-icons')
include ':react-native-vector-icons' project(':react-native-vector-icons').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-vector-icons/android')
Import the dependency: import com.oblador.vectoricons.VectorIconsPackage;
and then add: new VectorIconsPackage() in getPackages() method.