@arnout.wind When you try to run the WebSDK and open the browser developer tools, do you see any errors? Also, are you using the CDN, Local or NPM version of Web SDK 1.4.2?
You should be using screenShare: true, within the Zoom.Mtg.init function [1].
1 - https://marketplace.zoom.us/docs/sdk/native-sdks/Web-Client-SDK/api-reference
Thanks