To use the “Screenshare” function on Apple macOS devices, it has to be enabled in the operating system. Depending on the version of the operating system version used, the path varies slightly. To enable the function, please follow these steps:

1.) Please open the systempreferences/settings of your macOS device.
2.) Please open the “Security” and afterwards “Privacy” section.
3.) In this section you will see an option called “Screen Capture” – Please enable this option for the particular browser you are using.

Note: Please note that for external browsers (Google Chrome and Mozilla Firefox), the camera and microphone must be enabled in the same area for the respective browser.

Source: macOS-manual