Have you verified the fuses that are on the generator itself?
Generally, if you have 12V at the generator starter solenoid, there are no DC fuses in the RV to worry about for the generator operation since the generator's DC power feed (for the control circuits) is taken from this point, rather than having a separate DC power supply for the controls. There's usually a DC fuse (or a few) for the lower-power control circuits.
If the fuses, etc. check out, it's possible the starter solenoid on the generator could be bad or have become disconnected, or something along those lines, though generally I might expect an error code to come up if that's the case.