Proteus VSM (Virtual System Modelling) comes with thousands of components, but it focuses on general-purpose ICs (741 op-amps, 555 timers, Arduino, PIC microcontrollers). Switching regulators like the LM2596 require complex transient simulation models. Unless you download a specific third-party library, you will see an error:

If you are designing a buck converter or a power supply module, you have probably searched for the in your Proteus software. You clicked on "Pick Devices," typed it in... and got nothing.

You can find high-quality symbols, footprints, and 3D models from these reputable repositories: SnapMagic (formerly SnapEDA) : Provides comprehensive symbols and footprints for the LM2596S-ADJ

: After adding the library, restart Proteus to load the new library.

If you get "Model not found" or "Simulation failed" errors after downloading a "top" library: