I'm making a map that uses custom sounds and scenes and each time I try to use the scenes, I get "Scene <path> missing!" I doubled checked the paths and they are they need to be but they still aren't loading.

I apologize for the late reply, but if you haven't already, go into the Face Poser and click "File > Rebuild scenes.image...". If the problem still persists, I unfortunately won't be able to help you since that solution has always worked for me.

Edit: You should probably move the original "Portal 2/portal2/scenes.image" to a different folder before rebuilding it, so only your custom scenes will be on the file and there's less of a chance of overriding any existing scenes.