Why doesn't Grenadier Realty Corp pay back security deposits?

Many landlords and management companies in NYC don't. You should consider the possibility of suing them for the deposit in small claims court (if the deposit is $5000 or less). If it is a building-wide problem, you and your neighbors should also consider contacting the NY attorney general's office. See also: http://www.dhcr.state.ny.us/rent/factsheets/orafac9.htm http://www.courts.state.ny.us/courts/nyc/smallclaims/forms.shtml