Ok, so I just encountered the same kind of problem. I can’t set a mesh to simulate physics through BP and can only set it through editor properties.
But I solved it.
What I did was I went to the Physics Asset the mesh is using and set the “Physics Type” property of the collision bodies to be “Default” instead of “Simulate”. Now I can enable and disable physics simulation at runtime through BP.
Note to devs: I think it must be mentioned somewhere in the “Set Simulate Physics” function’s description.