The Family Share program doesn't allow the sharing of in-app purchases. 

For more information follow this link:

Therefore, to be able to share them, you must do the following in each of the devices with blocked access to the in-app purchases:

1. Uninstall the app from the device.

2. Exit the Apple account, tapping: Settings, in the device's menu > Apple ID:... > Sign Out.

3. Log onto the Apple account that made the in-app purchase: insert your Apple ID and Password > tap Sign In.

4. Download the app again.

5. Open the app and enter the in-app Settings (gear icon or "i" icon > tap the "Restore Purchases" button.

6. There! The packs should now be unlocked. 

Once the purchases have been unlocked repeat steps 2 and 3 to change the Apple ID back to the one held by the person who uses the device.