Try adjusting the cable tension setting a bit tighter, that should help it make the step, then check that the chain clears the cage when feeding from the various cassette cogs you'll use the middle ring with. You might have to fiddle a bit to find the best balance between shift response and chain clearance.
Once you've got the middle ring shifting OK from both directions, use the H and L limit screws to set the final trim on the inner and out rings.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.