So I think you’re in the same boat as @mac77bear in terms of wiring configuration. I’ll post that thread below.
So right now you have a hot and neutral in the lower box. We need to get a hot and neutral to the upper box to power the other Inovelli. You have two conductors passing through the light that you can use to do that, the red and the black/white.
The upper box is really the load box (the black in that box goes to the light), so that box will have the Inovelli controlling the load.
At the lower box, put the line and neutral back into the Inovelli and unbundle what I had you temporarily do. Using the 2nd line and neutral holes, connect the red to the line and the black to the neutral. This will send the line and load to the upper box. This switch will not have a load. The white from that 3-wire should already be pigtailed to the neutral bundle in that box.
In the upper box, red to line and white to neutral. Black to the load.
So now the upper switch will control the load as a 2-way. You’ll have to use binding or automations for the lower switch.
Here is that other thread: