FAILED CONFIGURATION: @BeforeClass setup org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Device 5210eea7b4e3a3ab was not in the list of connected devices

The problem : i am getting the error which i never used to get on my appium suite. Error : FAILED CONFIGURATION: @beforeclass setup org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Device 5210eea7b4e3a3ab was not in the list of connected devices (WARNING: The server did not provide any stacktrace information) but the device is in the list

When i try to run any android test, i am getting the above error. Which i never used to get it. We have app just like shareit and we need two phones both communicating on different port and we test it using appium
Environment

git version : git version 2.11.0 (Apple Git-81)
Appium version : 1.6.3

Desktop OS/version used to run Appium: 1.6.3
Node.js version (unless using Appium.app|exe): v7.2.1
Mobile platform/version under test: 6.0.1
Real device or emulator/simulator: Real Device
Appium CLI or Appium.app|exe: Appium CLI

Details

When i try to run the test on any android version i have started getting the error before they were working fine and were able to initialize the app but now i am getting FAILED CONFIGURATION: @beforeclass setup. i tried debugging the issue but i did not find any error in the app.
Link to Appium logs

@sidharth_lala, If you cannot able to see any errors in console output, check TestNG generated reports once. You might get some clue.

[quote=“SireeshaSimakurthy, post:2, topic:17860”]
rts on
[/quote]it contains the same error which it is giving on the console. can you tell me the location where this error file is located which is generated by TestNG.