Using Cordova with Phaser 3 and using Image Not Appearing in Browser

Phaser 3
1

I was working on this tutorial:
https://gamedevacademy.org/creating-mobile-games-with-phaser-3-and-cordova/

When I tried loading images using the below code:

function preload() {
    this.load.atlas('sheet', 'img/sheet.png', 'img/sheet.json');
}

function create() {
    this.add.sprite(400, 300, 'sheet', 'planeBlue1.png');
}

but the image doesn’t load. Only black empty screen is visible. No errors in console.