Troubleshooting Guides
These guides map directly to your health check steps (DNS → TCP → Auth → List) so users can fix issues fast.
- DNS resolution failed — Why FTP/SFTP DNS lookups fail and how to fix hostname resolution issues quickly.
- TCP connection timeout (firewall issue) — Why FTP/SFTP connections time out and how to diagnose firewall, routing, or allowlist blocking.
- TCP connection failed — General TCP failure causes when connecting to FTP, FTPS, or SFTP services.
- Authentication failed — Why FTP/SFTP authentication fails and how to correct credential, key, and account policy issues.
- SFTP directory listing failed — Why SFTP connects but cannot list directories, and how to fix path, permissions, and chroot issues.
- FTP passive mode firewall issues — Why FTP PASV fails behind firewalls/NAT and how to configure passive ports correctly.
- SFTP connection refused — What “connection refused” means for SFTP and how to fix port/service/firewall issues quickly.
- FTP connection refused — Why FTP servers refuse connections and how to diagnose port, service, and firewall issues.
- SFTP permission denied — Why SFTP returns permission denied errors and how to fix file or directory permissions.
- FTP data connection failed — Why FTP data connections fail and how to troubleshoot passive and active data channel issues.
- FTP directory listing timeout — Why FTP directory listings hang or timeout and how to resolve passive mode firewall problems.
- FTP passive mode not working — Why FTP passive mode fails and how to configure passive ports and NAT correctly.
- FTP EPSV error — Understanding FTP EPSV errors and how to resolve extended passive mode problems.
- FTP TLS handshake failed — Why FTPS TLS handshakes fail and how to troubleshoot certificate and encryption problems.
- FTPS certificate error — Why FTPS certificate validation fails and how to fix expired or mismatched certificates.
- SFTP host key verification failed — Why SSH host key verification fails and how to resolve known_hosts conflicts.
- SFTP authentication failed — Why SFTP authentication fails and how to fix password or SSH key issues.
- FTP login failed — Why FTP login attempts fail and how to resolve credential or account issues.
- SFTP subsystem request failed — Why SFTP subsystem requests fail and how to configure SSH servers correctly.
- FTP SSL negotiation failed — Why FTPS SSL negotiation fails and how to fix TLS configuration issues.
- FTP connection reset by peer — Why FTP connections reset unexpectedly and how to diagnose firewall or server termination issues.
- FTP server not responding — Why FTP servers fail to respond and how to diagnose network, service, or routing problems.
- FTP port 21 blocked — How to diagnose and fix firewall rules blocking FTP port 21.
- FTP timeout during transfer — Why FTP transfers timeout and how to fix idle timeout or firewall issues.
- SFTP connection timeout — Why SFTP connections timeout and how to troubleshoot firewall or network issues.
- SFTP connection reset — Why SSH/SFTP sessions reset unexpectedly and how to diagnose network or server issues.
- SFTP port 22 blocked — Why port 22 blocks SFTP access and how to fix firewall or security group rules.
- SFTP chroot permission issue — Why SFTP chroot jail permissions prevent access and how to configure directories properly.
- FTPS explicit vs implicit configuration — Understanding explicit vs implicit FTPS and why incorrect configuration causes connection failures.
- FTP anonymous login disabled — Why FTP anonymous login fails and how to configure server access policies.
- FTP server requires FTPS — Why plain FTP connections fail when a server requires FTPS encryption.
- SFTP key authentication required — Why SFTP servers require SSH key authentication and how to configure keys correctly.
- FTP transfer stalls — Why FTP transfers stall mid-transfer and how to troubleshoot data channel issues.
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