Help! Orbital Particles in 2018.1 - Play in scene, game, but not in build

Hope someone can help. All I find searching on this is other people with particle problems!

I got a great demo going using a script from Unity docs - you can find it here:
https://docs.unity3d.com/ScriptReference/ParticleSystem.VelocityOverLifetimeModule-orbitalY.html

Controls work great, particles start up on awake in scene and game. But a Mac OSX build does not show particles.

I found another script example that plays and pauses, stops emitters with a GUI - all work well except in a build.
https://docs.unity3d.com/ScriptReference/ParticleSystem.Play.html


Has anyone got a fix for this? You can probably duplicate it just by using that first script I linked to.

Thanks!