For proper particle display you need two things: a Display operator in your event and a compatible 3ds max display driver selected. tyFlow only has official support for Nitrous D3D 11 and OpenCL display drivers. All other drivers (ex: Nitrous D3D 9) may result in no particles being drawn in the view.
You can change your viewport display driver settings by going to the Customize > Preferences > Viewports tab within 3ds max.