I just purchased Sky Safari Pro 6 from the Apple App Store on my wife's iMac as she had some credit on her account. I also purchased the two available in app purchases of the PGC Extension and the UCAC5 Extension. All worked and installed. My wife and I have a shared family account with Apple. Because of this I can download and install Sky Safari Pro6 on to my Mac Book Pro. This works fine too, however when I click to restore purchases nothing happens. I log out log back in on my MBP and try again, nothing happens. So I figure since my MBP is set up with my Apple ID perhaps I need to create an account for my wife on my MBP and then log in as her with her Apple ID linked to that account since that is where the original In App purchases were made. I do this. Open up Sky Safari Pro 6 and try to restore the InApp purchases but now I get a dialog box to log into the App Store but the field for the Apple ID is filled with my Apple ID not my wife's so I cannot change it. I log in anyway with my Apple ID and try to install the in App purchases but no dice.
So how do I make this work or do I have to buy the in app purchases all over again..... which IMHO is ridiculous.