Quite simply, the Volume tab isn’t there on some .blend files.
Here’s an example:
With Volume option: https://gyazo.com/d7b02dbf58717206b43619922fd3b9fa
Without Volume option: https://gyazo.com/d7b02dbf58717206b43619922fd3b9fa
I’m not sure if this is a bug, or me being stupid.
So bacially, when I start the .blend file, it’s usually not there. But then it spontaneously appears out of random during editing. Sometime I have to close out of Blender, sometimes I have to play around with tabs. I’m obviously very confused by this. lol
Anyways, all help is greatly appreciated!