I installed primary switch (GE 12722) appropriately. One hot (line) wire, one neutral , one load (black) and one traveler (red). I am not sure how these connect but it seems they connect to light because second switch has 3 wires only from one cable (while,black, red). These connect well with standard switch and it works.
My problem is connecting the add-on switch (GE 12723). The switch has connection for traveler and neutral. I connected white pigtail with other neutrals from other switches and then to add-on switch. Both red and black have current. Which do I connect to switch and what do I do with other one? There is no extra black wire as in videos I have seen. Just those 3 wires. I have tried different connections without success. Thank you in advance to anyone that can assist.
See attached diagram.
I can see capping the black cable but there is no extra black cable in the primary box. I tried capping the black one in the add-on before with no success. I’ll try again. Thx!
It sounds like you might have misidentified your wiring and that you have a configuration that is different from what you described. You need to positively identify all wires in the circuit.