Electron not loading CSS file

I'm trying to load a css file in electron. I found other people with a related issue, their solution doesn't solve a thing for me. When I open my devtools it says:

Failed to load resource: net::ERR_FILE_NOT_FOUND index.css:1

And when I hover over the index.css it does in fact show the correct file location, it says:

file///C:/Users/myusername/myproject/src/assets/css/index.css

This file path corresponds 100% correctly with the path to my css file. My code is as follows:

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>My Project</title>
  <link rel="stylesheet" href="assets/ccs/index.css">
</head>

<body>
  <h1>This is just the beginning</h1>
  Great things to come
  <script src="../renderer.js"></script>
</body>

</html>

I've tried changing the link to href="./assets/css/index.css" as well as just "/assets/css/index.css", didn't change anything.

And js code:

const { app, BrowserWindow } = require('electron')
const path = require('path')

let mainWindow

function createWindow() {
  // Create the browser window.
  mainWindow = new BrowserWindow({
    width: 800,
    height: 600,
    frame: false,
    webPreferences: {
        nodeIntegration: true,
        enableRemoteModule: true,
        preload: path.join(__dirname, 'preload.js')
    }
  })

  mainWindow.loadFile('src/index.html')

  mainWindow.on('closed', function () {
    mainWindow = null
  })
}

app.on('ready', createWindow)

app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

app.on('activate', function () {
  if (mainWindow === null) createWindow()
})

I've been looking at this for hours on end and can't find what is wrong, the code is based off of electron's starting guide so I assumed it would work. If anyone could help me out here I'd greatly appreciate it!

EDIT: My file structure tree

+-- src
|   +-- assets
|        +-- css
|             +--index.css
|   +-- index.html
+-- index.js
+-- package-lock.json
+-- package.json
+-- preload.json
+-- renderer.json