Once you have successfully installed the plugin on your mac. If you performing a call and would like to share your screen (or a specific window), due to restrictions put in place in macOS 10.14 and above, you will need to authorize the specific permission "Screen Recording" in System Preferences.
1. Open System Preferences
Go to "Applications" or use an App launcher: Cmd+Space, "System Preferences"
2. Search or Click on "Security & Privacy"
3. Activate SightCall in "Screen Recording"
Scroll down to Screen Recording on the left and activate SightCall (make sure to unlock in the bottom left before doing so).
Note that SightCall might not appear in the list until you first make an attempt to share your screen during a call, as the permission might not be requested before then.
4. Restart SightCall
You can do so by reloading the page where you are using SightCall