Becky,
Can you shed some more light on this issue? Is there any solution yet? This is a common occurence on iPhones of all models and it has happened for a while now on a few of my friend's phones, as well as my wife and my phones.
Essentially, when you pick a song to use as an alarm, just as we used to, it now defaults all of those songs to the default "Radar" tone sound, even though your songs ARE, in fact, downloaded to your phone's hard drive (NOT in the cloud because we don't use Apple Music and can confirm the songs are on our phones), even when we pick a new song from the internal storage of the device itself, it still plays the default "Radar" sound instead.
This is clearly a glitch and has been going on for a while now. Any fixes yet?
One more thing to note, it is possible that the transferring beteeen phones after purchasing a new phone and adding those same songs back into the library caused and issue because the checksums of those two files (where the ringtone was searching for the song and the new song downloaded to the phone) are different and that is confusing the device.
Please note, this is no simple user error navigating the settings and menus. I am a power user and this issue cannot be resolved without intervention from Apple. Please pass this on to your superiors as it is a real problem.