Sawtooth wave generator not working in simulation
Try increasing the supply voltage to maybe 10 volts. – Andy aka


  @Andyaka It worked! I really can't see why it had to do with supply
  voltage, would you mind giving a glimpse of the reason we had to
  increase it? – Hilbert


I believe that the reason it worked at 10 volts is because the hysteresis levels around U1a coupled with the inability of the opamp to drive close to the limited positive rail were just fighting against running at 5 volts. It might work at 6 volts of course but, a rail to rail output opamp would be better.