This is about the new play system.
When i use simulate in 4.4 or before versions i can see instanced meshes. With 4.5. I can’t. So when i use simulate, as i have a quite only instanced mesh level, i have… nothing 
Which is a bit helpless to debug ^^
Then i use play in viewport, alt + s to simulate. It works ! but i have to travel in a large level and more :
Then the character begin to walk back and, or he falls or he stucks in a wall. so, when i try to possess, it does not work.
Then i have to quit and simulate is selected and i have to select play in viewport again because simulate will not work and then alt + s again.
If instanced meshes were appearing as before it would be ok. May be this is only a bug on my project upgraded from 4.4 to 4.5. If yes, i’ll try a migrate to a new project.