I have some files in a separate Godot project that I wanted to use in my current project. They include both scenes and C# code. After copying a whole subdirectory into my new project, I opened one of the old scenes and found that none of the nodes with attached c# scripts that have [Exported] fields are showing up in the Inspector. Even if I create a new scene, add a Spatial node and attach one of my C# scripts, none of the fields are displayed. The fields are showing just fine in my older project, so I'm not sure what's different in the copied files.
How do I fix this?