Git Repository Clone Failed? Troubleshooting "fatal: unable to access" Errors

`fatal: unable to access` errors are common and caused by network issues, incorrect addresses, permission problems, proxy settings, or cached credentials. Troubleshoot using the following steps: 1. **Network Check**: Use `ping` to test connectivity to the repository domain name. Switch to a public repository or mobile hotspot to confirm network availability. 2. **Address Verification**: Re-copy the repository address (distinguish between HTTPS/SSH) and paste it into a browser to verify accessibility. 3. **Permission Issues**: Private repositories require authentication. For HTTPS, enter account credentials (or configure credential caching); for SSH, ensure SSH keys are pre-configured. 4. **Proxy Configuration**: In internal networks, check proxy settings and configure `http/https` or `socks5` proxy addresses or disable proxies if unnecessary. 5. **Clear Cache**: Remove outdated credential caches and reset `credential.helper` to avoid repeated incorrect input prompts. Following these steps will resolve 90% of cloning failures. If issues persist, contact your administrator or upgrade Git before retrying.