Chrome Extension pop-up is blank

I recently uploaded a chrome extension to the chrome store. It was approved, but when I installed it from the store, it only displays a small blank box like in the image below.

It probably has something to do with the way I am uploading the files. Below I have put how I uploaded them, and the manifest.json. Any ideas?

  "manifest_version": 3,
  "name": "Reminder-App",
  "version": "0.3.0",
  "description": "Reminder app for all your tasks",
  "icons": {
    "128": "tasks.png"
  },
  "action": {
    "default_popup": "./build/index.html",
    "default_title": "Reminder App",
    "default_icon": {
      "16": "tasks.png",
      "24": "tasks.png",
      "32": "tasks.png"
    }
  },
  "permissions": ["storage"]
}

I compressed the build folder, the manifest.json, and the png from the image below into a zip file.