I believe I've been to the J condo in Dumbo. I think the problem is the neighborhood. The building, itself, is fine. From what I remember of my visit, there's a lot of people loitering around, it's next to the bridge, there isn't a good grocer w/in walking distance and there's a huge parking lot next to the building. I believe some of the surrounding buildings have been sold, so there may be some conversions or new development in the future. Try adding incentives to the buyers, buyer's brokers or to the renters. Your agent should have mentioned these incentives. If they can't, then contact me.