How do I transfer my purchased ringtones to my iTunes library

I purchased new ringtones from my iPhone 6+ and they don't show up on my phone. I connected the phone to iTunes in attempt to transfer the purchases to my computer. These are the screens that appear.

This first screen shows all of the tones that I have purchased. Some have already synced to my phone from previous purchases. I then selected a ringtone then "ADD TO" button - see next screen

This screen allows me to view what's in my library and those I've purchased. See next screen

When I add to library, the system does not let me complete the request (next screen)

I get this next screen and am stuck. Does anyone have an answer to this dilemma?