Check first the network connection:
You need to have a good Service and/or Wi-Fi.
If they are On, turn Off Hotspot & VPN.
Charge the battery > 70%.
See also -> If you can't connect to the App Store, iTunes Store, or other Apple services
If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support
-> If you tried all of the above steps and you still can’t connect, contact Apple Support.
Then try to redownload.
See -> Use tones and ringtones with your iPhone, iPad, or iPod touch
Use tones and ringtones with your iPhone or iPad - Apple Support
If you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK)