A possible solution for this is that you most probably not bundling your application first, perform the following steps and then deploy your app-debug.apk to your device
$> cd myproject $> react-native start > /dev/null 2>&1 & $> curl "http://localhost:8081/index.android.bundle?platform=android" -o > "android/app/src/main/assets/index.android.bundle"
(if the folder
assets does not exists create it)
Then run from project root
$> (cd android/ && ./gradlew assembleDebug)
install the created apk to you device, from location:
let me know if that fixes your issue