Windows Defender or third-party antivirus software often flags the constant stream of small .tar.bz2 files as suspicious. Temporarily disable "Real-time protection."
Locate the folder where you saved the Cygwin downloads (usually a folder named http%3a%2f%2f... inside your downloads). inside that folder. Restart the setup-x86_64.exe and try a fresh mirror. The "Command Line" Workaround cygwin download incomplete error
If an HTTPS mirror is failing due to SSL handshake issues, try a standard HTTP mirror. Use the "Use System Proxy" Setting inside that folder
Don't just click the top link in the list. Use the "Use System Proxy" Setting Don't just
If you are on a corporate or school network, the Cygwin installer might not automatically detect your gateway. Launch the setup. Reach the screen. Select Use System Proxy Settings .
If that fails, select and enter your network credentials. Clear the Local Package Directory