Thanks for the reply. The gift product is just a simple product — no variable products involved. It’s set as a gift and the giftable form shows up fine and adds to cart as a free product.
I agree that it’s most likely a conflict with another plugin. I tried giftable earlier in development and didn’t have the same issue.
I’ll mark this as resolved because it’s most likely a problem on my end. If I find a solution I’ll give you an update here.