Unable to view content despite Family Sharing & Purchase Sharing both turned on

If you can't find your family's shared apps and content - Apple Support

What you can do with Family Sharing - Apple Support

How to share apps and purchases with your family - Apple Support

Members of a Family Sharing group are indeed expected to each sign in using their own Apple ID account, as used to join the group, to access any shared purchases, such as movies from Apple’s iTunes Store/​Apple TV Store. From the TV app Library, go to Family Sharing, then to the person/​Apple ID that made the purchase, then to the title.

Verify if there are known outages. System status - Apple Support

Else try signing out for the account, then sign back in, to refresh the loading of account properties.

Else try restart of the Mac (or other playback device).

Else try some Mac troubleshooting:

• How to use safe mode on your Mac - Apple Support. ‘Safe mode’ can help you to determine whether an issue is caused by (non-default) software that loads as your Mac starts up.
• How to test an issue in another user account on your Mac - Apple Support. If an issue stops happening when you log out of your macOS user account and log in with another, the issue could be related to the files or settings in your user account.

Let us know the results of these tests.

If the issue persists after that, then I would suggest to contact an expert from the Apple Support staff for further assistance. Contact Apple for support and service (phone numbers) or start your support request online (chat/​email/​callback).