I have a family plan for Apple Music. My daughter in in my family but how can she use the Apple Music subscription

Make sure the software is up to date on all devices involved.

Update macOS on Mac - Apple Support

Update your iPhone or iPad - Apple Support

If you see a message saying to try again later, see if it's a system issue: Apple - Support - System Status

Sometimes it helps to have the devices involved take a fresh look at settings:

● If this is a service, try disabling it and turning it back on.

● Try signing out of accounts and back in again.

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

Sign in with your Apple ID - Apple Support

If you have more than one Apple ID, don't forget you may be signed into other accounts too for special services such as iMessage and Media & Purchases.

● Restarting is a simple step that can resolve many unexpected behaviors.

iPhone: Restart your iPhone - Apple Support then choose your model.

iPad: Restart your iPad - Apple Support

Mac: Ways to start up your Mac - Apple Support

Try using other equipment if possible. I have seen several cases where somebody tried to do something on one item of equipment and failed, but then tried on a different item of equipment and succeeded.

Sometimes it can take some time for changes to propagate through the system and waiting may help ( e.g., Family Sharing of Apple News+ - Apple Community ). If a problem persists, particularly over several days, try contacting Apple for assistance:

Click here --> Choose your country or region - Official Apple Support Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

or:

"See a list of Apple phone numbers around the world."

Click here --> https://support.apple.com/HT201232

She would just need to open the Music App on her devices, and tap on the "Listen Now" tab. It should automatically detect the shared subscription and allow her to play anything from there.