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.
Ensure That Virtual Cam is Installed and Activated
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.
Ensure That The System Extension Isn't Blocked
Once installed, macOS will automatically block the newly installed extension, and then prompt you to unblock it. Click Allow in the Privacy & Security section of the System Settings application to complete the installation.
Note that some users may see a Details... button here instead of an Allow button. This could happen if you have other System Extensions or Kernel Extensions installed that need attention. Click Details... and then ensure that Ecamm Live Virtual Cam.app is activated.
Some users may also see a message here about changing security settings in "recovery mode". If you see this, it is likely referring to a third-party kernel extension that has been previously installed but not activated. Ecamm Live Virtual Camera is not a kernel extension and does not require security settings to be changed in recovery mode.
Chrome
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.
FaceTime
If you've just installed Ecamm Live's virtual camera, rebooting the Mac may be necessary before FaceTime recognizes it.
Ensure that Ecamm Live is Up To Date
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.
Ensure that Virtual Cam Is Ready
Make sure Virtual Camera in Ecamm Live's Output menu is Ready. If it's not installed yet, it will prompt you to install.
Quit and Reopen Video Apps
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.
Restart The Mac
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.