HTML5 Atmospheric Fog missing when packaging

I’m brand new to UE4 and have just followed the beginner tutorial to get started building the basic structure with the table and chairs inside it.

I packaged it for HTML5 and ran it in Safari (I’m on a Mac) and everything is there except for the atmosphere. It’s all black, There’s no sun or sky, although the shadows from the sun are all being projected in the environment.

The strange thing is when I change the settings so the default level is the minimal level (the one with basically just a table and chairs on a grey slate and atmosphere around it) and package it in HTML5 the sun and sky are included.

I only get this with HTML5 not when I package for Mac directly.

Is this simply because I shouldn’t be running it in Safari?