Tube is lit and the LEDs are glowing on the B side, so it is likely the tube is regulating. But no voltage to speak of at D1 says it is not. The fact that the voltage is not exactly zero suggests that D1 is not shorted to ground, but rather is not getting any current fed to it.
Hard to know, but start by checking the connections to OB. One goes to D1, another to + reg B and from there to b reg B. Also of course check the soldering at D1; re-wet the joint if it's suspicious.
And while doing this, keep your eyes open for anything else that doesn't look right. Check the resistors at D2 and D7; they should be 220 ohms from D2 or D7 to ground. Those resistors are a bit fragile.
