I wired my HS210 exactly as I took the 3way switch out: tied the white neutral from the HS210 with the bundle of neutrals, green to bare copper (ground), the two traveler terminals to the red and black travelers from the old switch, and the last black wire (line/load) to the line/load terminal block onto the HS210.

Lights power on normally but when either switch is in the "off" position the light fixture blinks on and off repeatedly nonstop (dims very low and fully energized) I've tried to flip the travelers, no changes. Switch between the line/load with other 2 travelers' wires still no change. I probably  should mention that the light fixture has 3 non-dimming LED bulbs. 

Anything else someone may recommend doing before I decide to return it?