LM2596 simulation models are famously absent from the default Proteus library. A user from 2015 on Texas Instruments' E2E forum asked for a Proteus simulation model, and a TI engineer confirmed, "MultiSIM or Proteus are not supported softwares".
3.3V, 5V, 12V, or adjustable (1.2V to 37V) Oscillator Frequency: 150 kHz fixed frequency Efficiency: Typically greater than 80% Why You Need an "Extra Quality" Proteus Library lm2596 library for proteus extra quality