Saw that post on the Kobo help forum. I emailed a copy of it to them and they sent me a new copy of the books and I was able to link them to my Kobo account
"I contacted pottermore with the problem and they fixed the issue months ago. They sent me an email with a link to my books as if given as a gift with a new date of purchase which fixed the problem. So contact pottermore and they'll fix it for you."