It's black as usual with Keychron so I'm guessing - touch a wire between the orange pin and the cyan diode and it should activate the dead key. If it does touch orange to pink pins, if that doesn't work solder a short wire between the pink pin and cyan diode. If the switch still doesn't work also solder a wire between the orange and green pins.
If orange to cyan doesn't work please post a pic with the shiny bit (right of the 2020 in this pic) over the dead key, hopefully something weird is visible.