Why doesn't this phase shift oscillator work?
Break the loop, insert a signal (Vin) as shown below and plot the AC response of the circuit from 10 MHz to 1 GHz and see what happens: -

I suspect that there will not be enough gain when the phase response is 0 degrees OR, try running the simulation for a longer time-period because sometimes, oscillators need some time to begin noticeably oscillating i.e. they do not start instantly. If you have the option, run the elongated transient response not from the estimated operating point but right from t = 0 i.e. there should be some provision in your tool to stop the tool calculating the DC bias points and &quot;unhelpfully&quot; beginning the transient point when those transients have settled down. On MC12 (my tool) it is shown here: -

I never run oscillators with that option ticked even though my tool annoyingly defaults to it. Maybe it's the same in your sim.