The Family Share program doesn't allow the sharing of in-app purchases. For more information follow this link: https://support.apple.com/HT203046
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 > iTunes Store and App Store > 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.