Signed apk is unable to ping/request from our api server Ionic v2

Android gets successfully build and deployed in debug mode. Then we want to release for production, the apk gets created successfully and signed successfully. When installed on the Android device using, it is unable to call one specific server APIs and not even pinging a server side API. Am I missing something?

In debug mode I can hit my api server successfully in ionic 2

Even the iOS build is working fine and hitting the API server ionic 2

Please let me know any advice to solve that issue.