We have two 5 year old Lab littermates - one bright as a button and the other, whilst a gorgeous personality, is a little lacking in the IQ department. The clever one worked it out more quickly than I did, to be frank, but the dim one gave up quickly when brute force didn't work i.e. trying the lift the bones out of the narrow end, rather than sliding them to the wider end. As 2 big dogs they had to take turns because it's mayhem otherwise. We now have a mutually beneficial system of the clever one playing the game on her own and when she lifts and deposits the plastic bones to get the treat underneath, we put a treat into the upturned bone or put one under the bone on the carpet. This gives the dim one a hunt of her own i.e. find the nibble in a pile of discarded bones.
Like the reviewer above, the dim one sometimes thinks the plastic bone IS the treat and they need to be wrestled off her (but they're very solid so quite indestructible) but on the whole, this unconventional version of the game works for us. Takes the clever one about 5 minutes so it's over very quickly. We do it 2 or 3 times with treats only under some of the bones. Would definitely try another version of these games because both dogs have found it absorbing in their own way.