Consult the following help articles from Apple to make sure you have Family Sharing set up correctly:
Share App Store, iTunes Store, and Apple Books purchases with Family Sharing
If you don't see your family's shared content
If after following the instructions in the above help articles you are still having trouble, please contact Apple's App Store support directly for further assistance. Since Apple operates the Family Sharing program and we do not have access to it, you will need to contact them to get the issue resolved.