I believe I have it wired as suggested.
Inovelli dimmer param 21 = 0 - No Neutral, 22 = 2 - Aux
SB1 always has the live wire. I took the line and one of the travelers and put them at the neutral. And the other traveler into the other port on the GE Aux switch.
SB2 - After doing the changes to SB1 it now has one live wire. At SB2 I put the non-live travler to SB1 into the traveler port. The live wire into the line and the load into the load.
With this setup at SB2 the inovelli can control the light, but at SB1 the GE Aux is not effecting the Inovelli smart switch.
That sounds correct, wiring-wise. How did you set the parameters, via a hub or at the switch? If at the hub, which one?
Sometimes parameters don’t “stick”. You can try setting 22 to an incorrect value and save. Then put it back to 2 and save. Also try an air gap reboot on the Inovelli.
I used HomeAssistant with zwave2mqtt to set and validate the parameters. I also set them to other values and back as I had heard that sometimes they don’t get set properly.
I did also fully turn off the breaker and back in a few times and I still see the same issue.
I have a house built in 1900 that came with substantial knob and tube wiring. Almost all of my knob and tube switches (including 3-ways) would switch the neutral, not the hot wire. When you disconnected everything and found one hot wire in the one box, was the light fixture installed as you found it? Was there a light bulb in the fixture? If you removed the light bulb it is possible that you will find that the only hot wire in your system is the black wire at the light fixture and you will have no hot wires at either switch box.