Unfortunately I had the same experience, once all the treats were out my pup chewed the sides off. He was savvy enough not to swallow any bits but it no longer works. When it was working I was really impressed with it, it is a fantastic invention but not sturdy enough for dogs that like to chew.
I bought one of these as my dog loves his dog pyramid and I wanted an alternative to keep him occupied. He had it for an hour and a half, got all the treats out but also chewed off a lot of the trim which is made of soft plastic. He swallowed this in pieces, and 48 hours later vomited most of it up. The rest, smaller bits, passed through his system. I would not recommend anyone give this to their dog as I do not consider it is safe.