Home Assistant Theme Background

I tried to add a custom background from a jpg image to my HA theme. i am using the MacOS Theme (GitHub - JuanMTech/macOS-Theme: 🎨 By JuanMTech -- Theme based on the macOS system-wide light and dark mode interface).
I added the following lines to the end of the macos.yaml file:

# Background
lovelace-background: center / cover no-repeat url("/local/themes/macos/background.jpg") fixed

I used the Visual Studio Code Add-On for editing. My image file is stored under “config/themes/macos/background.jpg”

But the Background isn’t showing up, when I apply the MacOS theme to any of my dashboards.
Any help is appreciated.

Ensure it’s here

macOS Theme:
  modes:
    light:
      # Header:
      lovelace-background: center / cover no-repeat url("/local/themes/macos/background.jpg") fixed

and

    dark:
      # Header:
      lovelace-background: center / cover no-repeat url("/local/themes/macos/background.jpg") fixed

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