Purchased ring tones no longer work after upgrade to iOS 11

Since my upgrade of my iPhone 6S to iOS 11 some months ago, my special ring tones no longer work. (I have waited this long hoping that this would be corrected in an update.)

The special ring tones (wife, family, friends) were purchased from the iTunes store and used to work in the previous iOS. They are still there on the iPhone. When I select edit of a contact to select the ring tone, it correctly plays the ring tone. I save that change. However, when that person calls me, my iPhone rings with one of the default ring tones — not the one saved for that person.

This problem is for all the ring tones that I had purchased.

How to correct this?

Thank you in advance for your help.