Ecamm Live needs special permission to share your screen. Without this permission, Screenshare mode and screen share overlays will only display your Desktop picture, regardless of what you've chosen to share.
When activating Screenshare mode for the first time, Ecamm Live will ask for this permission. On macOS Monterey and below, you will see this message.
On macOS Ventura, Sonoma, and Sequoia, it will look like this:
To change this permission at any time:
Instructions for macOS Ventura, Sonoma, and Sequoia
Open the System Settings app, in the Apple menu.
Scroll down to the Privacy & Security section and click on it.
Scroll down to the Screen & System Audio Recording section and click on it.
Toggle the switch on for Ecamm Live.
You will be prompted enter your Mac's admin password.
Instructions for macOS Monterey and below
Open the Security & Privacy section of the System Preferences app.
Pick the Privacy tab.
Scroll down to the Screen Recording section in the left-hand sidebar.
Click the orange padlock to make changes, and enter your Mac's admin password when prompted.
Check the checkbox for Ecamm Live.
PRO TIP: Upon checking the checkbox, you'll get a message prompting you to quit Ecamm Live for changes to take effect. Click the Later button, as there isn't actually any need to quit Ecamm Live. You should see the screen sharing begin immediately in Ecamm Live