Same happened in my non-NYCHA Brooklyn apt -- stuff happens. Landlord finally got somebody to look into it today, and temperature just got up to 66°F for the first time in 4 days (turns out that 3-season sleeping bag I've had stored away for a couple decades can come in handy)! Hallelujah! I might actually hazard a shower in the morning if this keeps up (went in to work today looking like I'd been on a bender since X-mas eve, lol!

I suspect a large proportion of NYC apartment buildings are technologically obsolete, particularly in their hvac systems. And if you are in a rent-stabilized unit, your landlord has no incentive to do any upgrades.