How Can I Stop My Havanese Puppy From Howling So Much?

Hello! We just brought home a 12-week old Havanese puppy last Wednesday. He is absolutely wonderful and incredibly smart…he doesnt mind his crate and sleeps 6-7 hours through the night without an accident. He feels completely comfortable with us (my boyfriend and myself) and is probably TOO attached to me since I have been home with him every day since he has been here. The only problem is that when we leave him in his playpen, he HOWLS and whines SO much. We leave him in there about 10-15 mins at a time, with us in the house and we have left for about 20 minutes since we got him and left him in the pen and we get back and we HEAR him howling and barking from down the hall by the elevators! He came from a farm in Connecticut, to downtown NYC, so the sights and sounds are definitely a huge adjustment to him, but he has been really good with everything else except being left alone. Anyone have any ideas or helpful tips?? I go back to work on Jan 9th and am scared to leave him.

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