This is a farm that I just built following the new iron golem spawning guidelines. It is built in the air in survival mode in a snowy mountains biome. I made a copy of it and switched to creative to show images and problems. After making sure it had both at least 20 villagers and workstations, I watched for about 30 minutes. Nothing spawned, not even a cat. I then went AFK for 10 hours and still nothing. I had also made a previous farm in the same world, and it was working, but the golems kept spawning in walls, on slabs, on glass, and leaves. When the copy of the world was made, I tried to tweak the farms (more villagers and beds and work stations) and still nothing. I then went AFK for 2 hours and came back to still find everything completely empty. I have no idea what is going on, but I hope this helps. These pictures are from the copy in creative mode.l