UE4's new Path Tracer issues - Fabric Translucency using SubSurface

See title, I can’t seem to get sheer fabric materials such as curtains or blinds working in the path tracer. Any advice appreciated? It seems to work perfectly in reflections which is the strange thing.

The reflection to the right has exactly what I’m looking for, with the fabric of this blind allowing light to pass through. But this is for some reason completely absent in main scene to the left

To note, this works fine in regular lit mode, but not in the path tracer, and I need the level of quality that the path tracer offers.

Any and all help and advice appreciated. I can share any settings or material setups on request. Although I’ve tried a few materials that would otherwise work fine in normal ray tracing. No dice for the Path Tracer sadly.

Have you tried to put the camera next to the mirror? So you look at the window from the same angle than what you see in the reflection? Maybe it’s just that black rendered plane causing problems? And to rule out it’s only the current camera position?

Just to check, have you set the blend mode and lighting mode as the screenshot below ?