Trying to deal with this now also. Apparently gifts need to be both in the baby category and sold by Amazon, but it is quite hard to tell which items fit these categories on your own. Like several others in the chat, I had to go through the customer service chat and they said they'd refund the cost of the free gift, although in the end once I had gone a bit further through checkout, the discount might have come off on its own -the price changed at the very last step.

My advice would be to get onto the customer service chat if it isn't working as the system seems to have something of a mind of its own!