This happens if you only copied the schematic graphic but missed the underlying SPICE simulation model. Ensure that your download source explicitly states the library is "Simulation Ready" or "Active Model," rather than just a dummy PCB footprint. Component Missing from Search

Once downloaded, extract the ZIP folder and copy both the .lib and .idx files. You need to paste them into the default Proteus library folder. Depending on your version, the path is usually:

Link an external .MOD or .SUBCKT PSpice macro to the component properties.