Not quite sure what it should be, but I don't think that there should be any connection to the "spindle sensor" pin. That's for sensing spindle position on a lathe for threading purposes, nothing to do with router spindle. I think you've wired the VFD so that it is forward-running only (no reverse, which seems reasonable) but there's no spindle start/stop signal from the board to VFD. I don't know how the Eding board and software handle for/rev or start/stop - I'm going through the same wiring design process with CSMIO/Mach3 and VFD which is a better-documented route.