Operating system: Win 10
Graphics card: GeForce GTX 1060 3GB
If using volumetric materials whether it's attached to an object or used as a part of the World shader, if you go into Orthographic view in realtime render with EEVEE, the scene goes black. It doesn't matter what light is used or if you're using an emission material, it stays pitch black in Ortho view. See gif below.