The firewall block method works... until it doesn't. Windows updates sometimes reset firewall rules. If Windows Update resets your firewall at 3:00 AM and you launch SolidWorks the next day, the program calls home, detects the invalid license, and enters "Zombie mode"—every save exports a corrupted file.
It is strongly recommended to turn off Windows User Account Control (UAC) and temporarily disable antivirus software that isn't on the official recommended list. solidworks 2016 solidsquad activator install