family sharing apple music

Hello, i have been using apple music as an individual subscription for over two years now. Lately i decided to upgrade to family plan to include my sister's phone. I set up family sharing according to the guides, added her as a member, and allowed her to use my apple music subscription. only when she opens apple music app on her phone , it asks her to buy a new subscription. I dont get where the problem is, i spoke to an apple support agent, and she blamed it on the software update, the problem persisted even after the update. any thoughts ??