App works in Android and IOS Simulator but not after release

I'm using React Native using PAHO MQTT JavaScript. My App works fine in simulator but when I release it, it has a AMQJS0007E Socket error:undefined.

If this is not the best place to post this issue, please forward me to a better project.

Thanks.

The whole description of my problem is on: [stack](https://stackoverflow.com/questions/60895132/app-works-in-android-and-ios-simulator-but-not-after-release)