I am looking to install only one smart dimmer DVRF—6L on a three way switch that also contains a 4 way switch. I have tried the wiring suggestions in the instructions with no success.

The dimmer switch is for the second floor hallway

Switch 1 (standard 3 way located on 1st floor)

Switch 2 (dimmer switch Lutron but not a smart switch)) this is were I would like to install the new DVRF—6L (second floor South end of hallway)

Switch 3 (standard 4 way switch also located on the second floor at the North end of the hallway)