Multiple boost converter voltage pulled down
If the source of Q1 is at 24 volts and the gate signal (Fsw1) rises from 0 volts to 12 volts then the top boost converter will never activate its MOSFET (Q1) try connecting Fsw1 between source and gate of Q1.

You might also stringly consider swapping the diodes (1N4001 types) with something that can handle switching voltages in the hundreds of kHz.