Sorry if my last response was not clear, but if your Logic project is not in surround, then the Immersive Plug-ins will not show up. So, this sounds like the correct behavior.
You need to use a surround project in Logic to use the Immersive Plug-ins, they are not compatible with stereo formats.
If you’d like to test if the plug-ins are showing up correctly, you’ll need to test this by creating a surround project in Logic.
