XPDI3-IW wiring help

[PeterJ962]

I'm trying to replace the 3-way switches for a hallway light.  I got a XPDI3-IW switch and 2 XPSS-IW slave switchs.  I can't seem to get it to work, even with a few different combinations.

I've got a slave box with a RED - BLACK - WHITE
The other slave box with a RED - BLACK - BLACK
The main box has 2 RED - BLACK pairs.

For the slave switches I put the red to the control, and the blacks and white to the line terminals.
The master switch I'm not sure.

Any help is really appreciated!!!

TIA!
Peter