Raytraced Reflections broken in particular scene

I’ve just upgraded a project from UE 4.27 to 5.2 and am having trouble with raytraced reflections in the scenes - they just aren’t appearing at all:

Is there anything beyond the PostProcessVolume settings that would explain this behaviour? I can create a new scene and have the reflections work just fine, so I’m unclear on what I could be doing wrong.

RT reflections were also working fine in 4.27.