Hello and ! I am seeing the same issue - almost the same issue over here. Perforce project, some things work in PPV and some don’t - the one that doesn’t seem to be working for me is AO:
Checked in the effects cave example scene and it works there (and in other projects I have created). I also tried copying over a working PPV from another project but no effect.
Engine version 4.6.1
Did you discover anything that would help? This is pretty worrying because I have no idea what else might be broken that we just haven’t noticed yet 
Cheers for any info!