[Zoom] Screen Sharing not working?

Enable Screen Recording permission in macOS

On macOS 10.15 Catalina, you need to allow Zoom access to screen recording to share your screen.

You can do this in your System Preferences.
Select the Security & Privacy option,
click the Privacy tab,
scroll down to Screen Recording,
and finally check the option for zoom.us. If the option is grey, click the pad lock in the bottom left corner.

Zoom video conferences allow you to share content including:

Entire desktop or phone screen
One or more specific applications
A portion of your screen
Content from a second camera
Whiteboard
A locally stored video
Audio played from device
iPhone/iPad screen

Notes:

The host can disable participants' ability to share their screen.
For Basic accounts, screen sharing is set to Only Host by default.
In a webinar, only the host, co-hosts, and panelists can share their screen.
If you're using the desktop client, you can show Zoom windows during screen share.