- Applied Rotation, Scale, Position
- Cleaned up the mesh
- Removed Doubles (merge by distance)
- Set the Origin to Geometry
Every other object in the scene and new objects all unwrap with no issues, so I don't think it's my UV settings. I've removed all modifiers and textures and shaders, but I still can't unwrap it. I know the object in question is one that I could easily recreate, but I'd like to know what happened before it happens to a much more complex object not so easily remade. I'd be grateful for any advice on this!
UPDATE: Thanks for testing the file, everyone! It helped me narrow down the problem (my nooooobishness) once I knew the file or Blender wasn't corrupt. For all of the other objects in my file, I could mark a seam in edit mode, click "A" to select all, and click "U" to unwrap the object in the UV editor. For this object, I had to click "UV">Unwrap to unwrap this object. I'm not sure why this object was different than the rest, but that's 'cause I a noob. I'm sure I'll learn what I did in time! Anyway, thanks again, everyone! –