Eh, Probably coz of this I can see AO ONLY in shadows 
How to turn it ON for areas covered by sun- directional light?
“Because the thing is this: AO in UE4 gets only applied to indirect lighting. So if you fake GI with point lights, its again direct light so the AO gets masked off in those areas = its not visible. UE3 did not have that functionality, so faking GI with point lights was easy.”