Hey there, JKasie.
I see that you're having some difficulty using Apple Music to add music to your iPhone 6s on iOS 11.2.1. When you tap the cloud symbol to download a song or album to your phone, it just spins. I'm happy to help.
How to check the storage on your iPhone, iPad, and iPod touch -- Check the storage on your phone. If the space is almost full, check the recommendations for optimizing your phone if it's provided. You can also delete any apps you don't use too often. They'll be available to re-download if you find you need it again.
Get help with iCloud Music Library -- If there's ample space available on your iPhone, follow the steps below:
First check iTunes to see if the song is ineligible for upload. Additionally, if you added the song to your library from the Apple Music catalog, it might no longer be available on Apple Music.
Check your Internet connection
Open Safari on your iPhone, iPad, iPod touch, or Mac, or a web browser on your PC, and go to any website to make sure you have a strong Wi-Fi or Internet connection.
If you can't connect to a Wi-Fi network on your iOS device, you can try using cellular data:
- Go to Settings > App and iTunes Stores.
- Turn on Use Cellular Data.
You might have to pay a fee to download over a cellular network. Contact your wireless carrier for details, and learn about cellular data settings and usage.
Let me know how that goes.
Take care!