Can you show the exact code you’re running and where you’re running it from?
I’ve personally done it like this successfully before, from a component that was on the actor:
GetOwner()->FindComponentByClass<UStaticMeshComponent>()->SetSimulatePhysics(true);
I have been struggling with C++ changes not being detected by the editor after compiling sometimes though, so if you’re sure your code is good then it might be worth just closing the editor and building from VS and then re launching the editor to see if your changes now take effect