Problem load wms

good morning:
I’m new to this and I’m just starting out, so first of all thank you very much for creating this channel and for helping people like me (a bit more clumsy).
I’m trying to add a wms to cesium.js through a script I made
const viewer = new Cesium.Viewer(“cesiumContainer”);

const provider = new Cesium.WebMapServiceImageryProvider({
url : “”,
layers : ‘0’,
proxy: new Cesium.DefaultProxy(‘/proxy/’)

// Add a WMS imagery layer
//const imageryLayers = viewer.imageryLayers;
new Cesium.WebMapServiceImageryProvider({
layers: ‘CONTACTS’,
parameters: {
transparent: true,
format: “image/png”,

// Start off looking at CANARY ISLANDS{
destination: Cesium.Rectangle.fromDegrees(
I have managed to preview the place I want but the wms is not visible. the globe stays