rated up to 200V trigger voltage, and due to a patent they were pretty much the only game in town for a long time. What I did see suggested to avoid trigger voltage problems was a compatible small flash on the hot shoe in manual mode used to trigger studio flashes through their optical slave cell.
A probably useful table for this kind of problems:
The thing I don't get with flash voltage compatibility (or not) is that it is possible to make a fully electronic camera and by including a component which costs very little, make it work with any flash ever made. Yet it would appear that some designers have chosen not to. I think this is very foolish.
I put this down to three possibilities: Paranoia, stupidity or a ploy by marketing people to get you to buy only their compatible products!
A camera like the RZ67 which doesn't have any special flash function except trigger it then a simple mechanical contact would be cheaper to make and would support just about any voltage. Is it possible that the polarity of the Youngnuo trigger reversed?