Phaser background colour doesnt change

I just finished the review of Phaser: basics Link. I finished all tasks correctly, but the background colour is not changing. this is my code for “config”. If I change the width or height I do see change in the game-window. BG color should become “plum”

const config  = {
  width : 600,
  height : 400,
  backgroundColor: 0xdda0dd,
  scene : {
    preload,
    create,
    update,
  }
}

const game = new Phaser.Game(config)

I went back to the topic of making a config code, and when I copy the code there, I do get the updated background.(plum)

const config = {
  width: 400,
  height: 500,
  backgroundColor: 0xdda0dd
}

const game = new Phaser.Game(config)

edit**: just found out it workds when I remove the scene propertie, but I dont understand yet why this is.