Question why has gravity stopped working

My gameobjects have suddenly stopped falling, they just sit in midair where they're spawned. Checked several things:
- the RigidBody is still there
- use gravity is on
- is kinematic is off
- all freeze options are off
There is no scripting going on. Once they're spawned I just let the physics engine take over.

These prefabs have been working for months. Why would they suddenly stop?

 

I've seen some complains about the physics simulation option being disabled when upgrading the project to a newer Unity version. Ensure the option Auto Simulation is enabled in Project Settings > Physics:

 

Rats, that's not it - the option is still on. Just to make sure, I turned it off, played the scene, turned it back on, played the scene. Everything is still floating up in space.

 

Check if there isn't any collision box in the way that make it hang. I had this kind of problem. A procedural map plugin I used were spawning a collision box after it was done and my character that used to start in mid air fall just hanged there.

 

Good idea. Couldn't find anything, though.