Using Apple Music on iPad
I subscribe to Apple Music, but whenever I try sign into it on my iPad I’m prompted to buy another subscription. Can I use my subscription on both my phone and iPad? If so, how?
iPad Pro 11-inch Wi-Fi
As long as you are using the same Apple ID on both devices, a single subscription should cover both. Perhaps this article will help:
If songs are missing from your music library after you turn on Sync Library - Apple Support
If you still need help with Sync Library, contact Apple Support.