December 2022
The function had worked briefly, but suddenly stopped. Make out still worked no problem. After switching the wall the closet was "built-in" into a spandrel (wide spandrel from "Snowy Escapes", maintaining "built-in" look) the function worked just fine.
March 2023
April 2023
I just realized I'm having this problem too.
April 2023
If you're ok with using mods to fix bugs and are on PC/Mac, you can check the approved mods thread for "WooHoo in Closet Fix".
The 'Make Out in closet' interaction seems to be working fine, so I copied whatever was making that work to the' WooHoo in closet' interaction.
May
I play on PC and have been having this problem as well.
June
I can confirm that this is still not working. I completely reset my game, built a new small lot with a closet and tried to get a married couple to woohoo in it. Still, nothing happens.
July - last edited July
l'll simply repeat what others have said: remove the wall in front of it as a workaround for now. It used to work with the wall, and some options still do work with the wall, but not Woohoo any more. (Or try the mod fix above.)