While the "free lifestyle" is enticing, it is critical to address the "Professional" aspect of Proteus 89 SP2. Legitimate licenses for Proteus Professional cost thousands of dollars. The version often shared on forums as "free" is frequently cracked software.

You can’t legally get “Proteus 8.9 SP2 Professional” for free unless it’s an official trial, student license, or educational version. If you need a free and legal alternative for Arduino simulation, try Wokwi , Tinkercad Circuits , or Falstad’s simulator .

: Enables flowchart-based Arduino programming for users who prefer visual logic over traditional code. Integration with Arduino 1.8 IDE

Proteus 8.9 SP2 Professional is a commercial electronic design automation (EDA) suite from Labcenter Electronics used for schematic capture, PCB layout and mixed-mode circuit simulation — notably the ISIS schematic editor and ARES PCB layout, plus the VSM (Virtual System Modelling) simulator that can co-simulate microcontrollers (including Arduino/AVR) with analog/digital circuits.

This is the trick. You need the specific ".IDX" and ".LIB" files for Arduino boards. (You can find these via open-source community repositories). Place them in the LIBRARY folder of Proteus.