Thank you for the reply. Getting further, I traced it out and there was a break continuity on pin 1. The light for the clock memory and the main light on the board light up but the nixies still don't turn on.
You said you replaced the IRF-840 at some point, Is there any chance you replaced it with an 840A instead of a plain 840? I'm asking because I remember somebody said they had a problem with their HV going wildly unstable when they tried to use an 840A. I'm not sure why it should matter (the specs of the teo parts are very similar) but for at least one guy it did.
Other than that, well, I'm not sure. Just the usual advice: look again for bad soldering, "tails" of leads sticking out, crud on the solder side of the board, etc. Try a factory reset if you haven't already.
Look into it later when the dust is clearing off the crater.