Thanks for the purchase but you won't be able to get the code you provided working using it - as per the listing of my resource, it is for adding oembed endpoints into the default ones provided by Invision, and providing access to those on a group-basis (if desired)
So, the question is: does Canva provide an oEmbed endpoint? If yes, great...use that. If it doesn't, then you'll probably have to use the iFramely integration provided by my resource.