It took almost pulling all my hair out (not literally) BUT I FINALLY FIGURED IT OUT!!!
For those of us that followed the instructions to a T but still no resolve? Here's the solution!!!
Go to settings
Settings
Notifications
Advanced settings
*Manage notification categories for each app
Go back to settings again
Notifications
App Notifications
Select the app you want to change (eg messages)
FINALLY
Click on Notifications categories
Make sure allow Notifications is enabled
Click incoming messages
Click on sound
And voila!!! Select the sound you want!
Whew! Hope this helps
