.Ring Pro - wired to stand alone transformer- resistor/ diode required?

There seems to be Mnuchin confusion as to whether the “Pro” requires a resistor for stand alone transformer. Instructions make no mention of needing one and another link seems to indicate a whether a diode is required ( a resistor is not a diode). Some have claimed that adding a resistor prevented Ring from starting ip. So which is it? Ring needs to do a better job of clarifying what products do and don’t need to install!