When you get a new Apple device, and depending on the data from how you set up the new device (previous backups etc) you will most likely run into Apples wonky restore system. Restore purchases doesn’t do anything here except sync the devices with the iTunes ID in use. You still have to download and install things. IAPs are tricky. Apple will still put you through the same process as a new purchase. However, as long as the iTunes ID being used is the exact same one as the original purchase, they cannot charge you again.
Accept the purchase and right after hitting ok, iTunes will follow up with a new message informing you the item was already purchased and can be download for free. If that message doesn’t come up, that means only one of two things, the iTunes ID is not the same as the original purchase, or it was refunded.
They can only charge repetitively for Live subscriptions so that’s a very different story.
Before anybody asks, yes I am absolutely certain of this. I’ve done it myself for years with every device change.
That should resolve things. :)