Here is the deal everyone:
It appears that custom ringtones need to be purchased and downloaded as ringtones (ringtones only - not entire songs).
This can be accomplished by opening the “iTunes Store” app on your iPhone running iOS 11. Next, tap on “More” (...) at the bottom right of the app. You will see a short list of custom ringtones - tap on “See All>”.
Pay $1.29 and and select “Set As Default Ringtone”.
Repeat this process to your hearts content, until you run out of $$, or don’t want to pay $1.29 for 30 seconds of a song (same price as the entire song, but you don’t get the entire song).
You can search (i.e. van halen ringtones, or the godfather theme ringtone, or sweet home alabama ringtone”, etc.) to locate your choices.
While the list of available ringtones is vast - you are stuck with whatever 30 sec segment of the song is cut out as the ringtone (older versions of iTunes let you pick your own 30 sec segment).
Greedy artists and publishing companies - gouging the fans - making us pay twice (once for the whole song and the same price again for the ringtone only). GFY
Your existing ringtones created with older versions of iTunes no longer work.
Anyway - hope that helps.
-Rob