Animation must be Legacy, but I can't set it as such

I made a single-animation mesh in Blender that just rotates.
Then I imported it into Unity. The mesh imported fine, but the animation wouldn't play even if I set it to play automatically.
I tried Fbx and Collada, and neither worked.
Then I noticed an error:

I looked up the error and found a way to set the animation to be Legacy.
However, it wasn't letting me mark it as Legacy, and I suspect that the file may have been read-only.
Can I get help with this? Thanks!

 

Select the model, go to its Rig tab, and set the Animation Type to Legacy.

 

Ok, I did that, but now the animation seems broken. Only the Z-facing polygons are rendering; the rest of the mesh won't show even if it has a material.
How do I fix that?

 

If the object in your scene was created before you changed the Animation Type, delete it and drag in the model again.

Otherwise I'm not sure, the Animation Type shouldn't be able to cause something like that. Maybe post a screenshot?

 

OK, that worked! Thanks!