I saw those Dogobies at the vendors section at a show earlier this year. I should of grabbed a couple then. Would be an easy thing for the min-pin to handle although I don't think there is anything he's afraid of...seriously...except for cold rain 8>)
I don't mean really "afraid", just maybe some dogs are sensitive about those hard/heavy thin things hitting their mouths. Can't blame them. Some dogs may just sensibly be wary of things (my dog was just plain afraid, generally, but still curious at what looked like fun).
Of course, it's possible you just have a dog who just plain isn't interested in it. But at $6/pop, it's not a bad thing to try and verify.