It says: Importing for this baby needs the Family plan

On the Free plan, a family logs one baby: the first one added. Importing for another baby needs the Family plan, and the access comes from the family's owner.

1. If you are the owner, tap the round Baby button at the bottom right. On the baby’s page, the same button opens Settings. Tap it, then tap Subscribe.
2. If you are a carer, ask the owner to check their subscription.
3. Then import the file again.