Ecamm Live's Virtual Camera feature is a great way to send the output of Ecamm Live to other apps on your Mac. The other app will list it as a webcam called Ecamm Live Virtual Camera. Here are some steps to try if it's not showing up.

Check the Virtual Cam section in the Outputs menu at the top of the screen. You should see a Ready or In Use menu item as shown below, which will indicate that it's installed and ready to be used.

If you see a menu item here titled Install Virtual Cam..., pick that to install or update the Virtual Cam system extension.

When installed, macOS will automatically block the newly installed extension. Refer to the installation instructions here to ensure that the camera extension has been enabled.

Virtual cams work great in Chrome. However, Chrome may not always refresh its list of cameras. After turning on Ecamm Live's Virtual Camera feature, quit Chrome, (choose Quit Chrome from the Chrome menu up at the top of the screen beside the  menu) and then re-open it.

If you've just installed Ecamm Live's virtual camera, rebooting the Mac may be necessary before FaceTime recognizes it.

Pick Check for Updates from the Ecamm Live menu at the top of the screen beside the  menu to ensure that you have the latest version of the Ecamm Live app.

Make sure Virtual Camera in Ecamm Live's Output menu is Ready. If it's not installed yet, it will prompt you to install.

If you've just installed Virtual Cam for the first time, you'll need to quit the app that you want to use it with and re-open it.

If Virtual Cam is still not showing up, and you've just installed it, restart the Mac. Then, open Ecamm Live, and then open your other app.