Popup shows refuse to connect, when I click EDGE extension icon

I want to display popup in my laptop EDGE browser in a specific url. Popup should be displayed as view like mobile phone browser or like mobile mode view.
Everything I implemented but popup shows “refuse to connect” when I click extension icon.

manifest.json:

{
  "manifest_version": 3,
  "name": "Example",
  "version": "1.0",
  "description": "An Extension that popup to example.com",
  "permissions": ["activeTab"],
  "action": {
  "default_popup": "popup.html"
 },
"background": {
"service_worker": "backgroundext.js"
},
"icons": {
"16": "icons/c16.png",
"32": "icons/c32.png",
"48": "icons/c48.png",
"128": "icons/c128.png"
}
}

popup.html:

<!DOCTYPE html>
<html>
<body>
  <iframe id="myFrame" src="https://www.example.com" style="display:none"></iframe>
</body>
<script src="backgroundext.js"></script>
</html>

backgroundext.js:

document.addEventListener('DOMContentLoaded', function() {
  var myFrame = document.getElementById('myFrame');
  myFrame.style.display = 'block';
});

Error:
[![refuse to connect][1]][1]

  [1]: https://i.stack.imgur.com/Daumr.png