Failed to get desired output of a pulse width modulation circuit simulation
If you ignore V1 then you have a classic op-amp/comparator relaxation oscillator circuit that you also find in this SE question:
Oscillator circuit with TL071 opAmp for amateur very short range AM radio
and these other web pages:

https://publicism.info/science/electronics/11.html
https://circuitdigest.com/tutorial/relaxation-oscillator-using-op-amp

The output will be a square wave with a period of about 75 uS between +12 and -12 (the op-amp supply rails)
When you add V1 you should get a frequency modulated square wave that looks like this:

Note how the time between the pulses increases and decreases every 2 milliseconds which corresponds to the 500 Hz frequency of V1.
I would first remove V1 and make sure you can get a square wave output from the classic relaxation oscillator circuit. I've had good results setting the pot to 25% or 75%.
You can also try using an ideal op-amp model instead of a 741.
After you get the relaxation oscillator working, then add V1.