We handle many support requests for people who purchased add-ons for Easy Books and want to use them on a new Mac. This is especially true just after Christmas, I suppose that's the peak time for sales of new Macs!
The process should be simple, just re-download Easy Books and click Already purchased on the add-ons screen. However, we sell Easy Books direct from the web site and Apple sell a version from their Mac App Store. The two editions are essentially the same, and each can restore purchases. But only those made in the same edition - whether Mac App Store or Web Site.
So what can go wrong?
The Mac and iOS apps are priced separately. Purchases made in Easy Books for iOS can be restored into other devices running iOS but not in Easy Books for Mac. The reverse is also true; purchases made in Easy Books for Mac cannot be restored in Easy Books for iOS.
Another common problem restoring purchases on the Mac is caused by switching editions. In other words you originally purchased add-ons from the Mac App Store edition of the app but downloaded the app from the web site to a new Mac. Or vice-versa. If you purchased direct from the web site edition, you will have received an order number from us, looking something like EB13120Y-3558-81122. Otherwise, use iTunes to review your purchase history with Apple.
The next most common problem only happens in the Mac App Store edition (and App Store under iOS). It occurs if you have changed your Apple ID. Apple will only restore purchases to the same Apple ID, and it isn't possible to move purchases linked to one Apple ID to another. In these cases the app must be deleted from the Applications folder, then the Mac App Store app is used to sign out, before re-downloading the app using the correct Apple ID.