From my understanding of the circuit, the 154V rectified ac voltage should be sufficient to start the switching regulator STR-Z2156 and produce secondary voltages. Then some feedback circuit via the optocoupler PC603 pin#4 would go low and enable the PFC function via stopping the conduction of Q623. IC601 pin#12 goes high and PFC runs and produce 380V on the rail, whereas switching regulator would response and maintains the correct voltages at the secondaries.
I'm sure at present pin#4 of PC603 is several volts w.r.t. the negative terminal of high voltage capacitor C616. If this is the case, then the PFC function is not activated.
The chance of switching regulator STR-Z2156 failure is high. Unfortunately, I couldn't locate a datasheet for this chip so I can't say for sure if it will work with 154V or not.