On Mac's, your computer will require some additional permissions in order to screen share. You can check those permissions with the following steps:
- Head to "System Preferences" -> Security & Privacy
- Click the "Privacy" tab. On the left, look for "Screen Recording" then on the right, make sure the browser you are using is checked. In this case, Google Chrome.
- That's it! Your browser now has permissions to share the screen. You may need to quit the browser and re-launch it for the new settings to take effect.