Requested device not found chromeMediaSource: 'desktop'

Question

I am trying to create a web application which can share the desktop with the system audio using webrtc from chrome browser and if I set the constraints :

const constraints = {
audio: {
mandatory: {
  chromeMediaSource: 'desktop'
}
 },
video: {
mandatory: {
  chromeMediaSource: 'desktop'
}
}
 }

I get this error "DOMException: Requested device not found" or "DOMException: Invalid state"

here is the demo: https://codepen.io/EbramTawfik/pen/xQozaE