I have family sharing and want to share my subscription of My Fitness Pal with my family members but it will not allow me to.

I recently purchased a subscription of My Fitness Pal and I want to share it with my family members who i already share my subscriptions with through Family Sharing. However, when my family members try to access the paid subscription, they aren't allowed too. Is it because i started a free one month trial and won't be billed until the month is up?