How do I simulate physics on a mesh?

I am trying to simulate physics on a mesh that I have made, but in the details tab of the component portion of the blueprint the check box for it is grayed out. What have I messed up?

In Details, set the component to have Transform > Mobility > Moveable ?
Optionally, click the Eye icon to the right of the Search filed and choose Show All Advanced Details.

And further down, under Physics, tick Simulate Physics.
The Mass value seems to be greyed out, but you can set Mass Scale, etc. in the advanced details.

If you want to have Hit events in your blueprint graph, tick Simulation Generates Hit Events.

Does your mesh have collision? Open it up in the static mesh editor and add some simple collision. Note you can also import this with the mesh assuming you’ve set it up in the FBX.

In the 4.5 release collision is auto-generated for you so this step would no longer be needed

hey ori cohen!! we have very similar names haha…
i’m using unreal 4.20 and still have the same problem even after i add simple collision to it in the mesh editor, i’ve generated the static mesh from a skeletal mesh that didn’t had physics asset set up.