UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36

Steps to reproduce the problem:
1. Open the Chrome webstore
2. Add this extension https://chrome.google.com/webstore/detail/pact-engine/ghnebihkloddbfjhhainedngckegndeg?hl=en-US
3. Try to run.

What is the expected behavior?
It has to run the accessibility test on the page

What went wrong?
Although it is working absolutely fine in Developer mode. Unable to run on chrome webstore.

Did this work before? No 

Chrome version: 67.0.3396.99  Channel: n/a
OS Version: 10.0
Flash Version: 

I developing Devtools extension by following this example from github. I am able to run the extension fine in the developer mode but when i moved the same to web store. I am facing the following issue This extension may have been corrupted. and found following console error :

(Uncaught TypeError: Cannot read property 'connect' of undefined
    at createChannel (messaging.js:13)

messaging.js:13 has this code 

(function createChannel() {   
    var port = chrome.extension.connect({
        name: "Sample" 
    });
    var count=0;
    var activeTabClass;
    // Listen to messages from the background page
    port.onMessage.addListener(function (message) {
		setTimeout(function(){showResult(message);},1)       

    });

and Manifest.json has this.

{
  "name": "Sample Engine",
  "version": "1.04",
  "manifest_version": 2,
  "devtools_page": "devtools.html",
  "description": "Chrome Developer Tools",
  "icons": { "64": "images/pact.png" },
  "background": {
    "scripts": [
      "scripts/jquery1.12.4-min.js",
      "scripts/jquery-ui.min.js",
     "scripts/background.js",
	  "scripts/panel.js",
	  "scripts/tab-order.js",
	  "scripts/high-lighter.js"	  
    ],
	   "persistent": false
  },
  "content_scripts": [
    {     
      "js": [ "scripts/jquery1.12.4-min.js", "scripts/jquery-ui.min.js"],
	  "css": ["css/Injected-styles.css"]
    }
  ],

  "permissions": [
    "activeTab",
    "tabs",	
    "http://*/*",
    "https://*/*",
	"storage"  
  ]
}