VFD Suddenly stopped working

If you have no green light and you have verified that it is getting 24v from the SO5 controller then the issue is in the VFD box. Did you buy the VFD a while ago? The newer PCB’s should have fixed this issue. What version of the VFD control PCB do you have?

If you have a older PCB version you can desolder Q3 and put a jumper across the emitter and collector as seen in the picture below(the soldering was done by C3D and not me).