Upside down? Right side up? Is the sphere suppose to be upside down with just the Refractive? I added the Solidify. Didn't really see any changes, then I realize Mix Shader was at 50%, slide it to the right and now see the edge of the sphere but nothing really. It did seem to become a lens and kinda zoomed in on the HDRI but nothing vertically challenged. Just curious if this is normal
Can you post some screenshots? I believe people have been confused by this in other occasions and it's just that the ground floor plane was throwing things off, if you turn it off and see all the refraction based on the background HDRI image world, you got all the goodies.
I've been going around the tree a bit with it. I posted this once before then discovered I didn't have the Mix Shader at 100% (helps to have this at 100% and not the default 50%. I think it's fine now, I was staring at too long. Now it looks right. It is upside down with just theRefracted. 
