chrome extesnion shows 50x50 icon

I would like to show my full-size banner when people search for our keyword but instead, Chrome shows 50x50 icon. we have uploaded all required size in the Chrome developer console here is screenshot what we are looking for.

https://imgur.com/a/59OIBMo

here is our manifest.json. Any help will be great

{
  "name": "sample app1",
  "short_name": "sample app1", 
  "description": "sample app1",
  "version": "1",
    "browser_action": {
    "default_title": "sample app1",
    "default_icon": "images/sandbox-16.png"
  },
   "icons": {
    "16": "images/sandbox-16.png",
    "48": "images/sandbox-48.png",
    "128": "images/sandbox-128.png"
  },
  "background":{
  "scripts": ["js/background.js"],
  "persistent": false
},
  "permissions": ["tabs"],
  "manifest_version": 2
}

All images are available in images folder but i think it is something with Chrome developer console but we have uploaded whatever image it asked and its not about time as we have already waited 1 day and tested in other computer also so it's not about cache.