Mac OS 10.15 Catalina has changed a security preference allowing applications to record your screen. In order to share your screen or other content in Collaborate Ultra, you will need to change a security setting on your computer.
Select the Apple menu on the top left corner of your screen. This will open a menu. From the menu select System Preferences.
This will open your system preferences. Select Security and Privacy.
This will open your Security & Privacy settings. Click on the Privacy tab and scroll down to Screen Recording. Check the box next to your preferred browser(s) in order to allow the browser to share and record your screen.
You will then be prompted to restart your browser.