Ok after trying version 4 I uninstalled v4 and v3 and reinstalled v 3.3.

Alle seemed ok, but after saving and closing the file I was working on and re-opened it, The viewport isn't showing the hair anymore. al well as the emitter.

Selecting the emitter in the outliner does show the modifier stack. Deleting all ornatrix modifiers do show the emitter object, 

Then when re-aplying the ornatrix hairsystem, no hair is visible

Rendereing doesn't work also?? :-(

Menno