Exponential Height Fog Not Showing On HMD


I’ve been using Unreal for a few weeks now and teaching myself using the forums and youtube etc so apologies if this is a stupid question… here goes:
So I set up a walkthrough project using the fps template and packaged it to windows which works great and I love it. I’m now working on the Oculus Go. I set up a new project (following all the settings advice etc) and migrated my model and copied in all my light settings etc. Project is built. When I launch the new project on PC is works great and runs exactly the same as my previous version. However when I launch the project on the Oculus Go the project switches on in the HMD, I can look around and everything comes through except the exponential height fog doesn’t show. I have noticed that the graphics seem slightly different as well but I’m not sure if this is my eye tricking me because there is no fog. I feel like it could be something in my settings or something to do with instanced stereo? Can anyone help?