Give the puppy a kong when you leave, and only when you leave, it can be filled with peanut butter, or frozen and filled with yogurt, peanut butter, it will give the puppy something to look forward to when you leave, and it will in time correlate you leaving with getting the treat. Also, put a favorite toy or stuffed animal with the puppy always when you leave, that and the treat should help. Freezing the kong makes it last longer and gives the puppy something to do. It will stop crying do not make a fuss over leaving, or saying goodbye, don't say anything, just leave like it is not a big deal, after you put the kong or treat in with the puppy.