Electronic Ballast Runs HPSV But Not MH Lamp

MH bulbs and SV bulbs are not made the same way and neither are the ballast that run them.

With an old-fashioned inductor ballast, you would probably get away with this, albeit with a mismatch that wouldn't do your MH bulb a lot of good.

Your electronic ballast is a lot smarter than an inductor ballast, and almost certainly has protection circuitry built into it, and it is this protection that is stopping the lamp from operating.

IIRC, sodium bulbs operate with a terminal (that's across the bulb ternimals) voltage of about 90V when new, and this rises to around 130V when the bulb is on its last legs. A MH bulb operates at about 145V when new, again rising as the bulb ages. The protection circuit will pick up on this and kill power to the bulb if it is too high.