This is the #1 error in Proteus 8.9. If the simulation freezes or says "Cannot connect to COM1":
However, always pursue legitimate software channels. The knowledge you gain from a legal copy—combined with the safety of malware-free software—is worth far more than any cracked version promising "Proteus 8.9 SP2 Professional with Arduino 1.8 free." proteus 8.9 sp2 professional with arduino 1.8 free