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General Troubleshooting – Nginx Proxy Manager

Introduction

This guide provides solutions for common issues encountered when using Nginx Proxy Manager in a Docker environment, particularly with SSL, port conflicts, and reverse proxy failures.

Port Conflicts (80/443)

Symptoms: - Container won't start - Logs show: Error starting userland proxy: listen tcp 0.0.0.0:80: bind: address already in use

Solution: - Identify the process occupying the port: bash sudo lsof -i :80 sudo lsof -i :443 - Stop or disable conflicting services (e.g. Apache, another Nginx) - Restart NPM: bash docker-compose restart

SSL Certificate Request Fails

Symptoms: - Let's Encrypt cert fails to issue - Error: Timeout during connect (likely firewall blocking port 80)

Solution: - Ensure port 80 is open to the internet - Temporarily disable Cloudflare proxy (DNS Only mode) - Use DNS Challenge + Cloudflare API token if public IP is dynamic

Wildcard DNS Challenge fails

Symptoms: - Cert creation with *.domain.com fails - Logs show DNS update timeout or token errors

Solution: - Verify your API token in Cloudflare: - Must have DNS Read + Edit for the zone - Ensure token uses correct dns_cloudflare_api_token=... format - Check DNS propagation time or set Propagation Seconds to 60

Admin Panel Not Loading

Symptoms: - UI is inaccessible via browser (http://ip:81) - Browser says “refused to connect” or blank screen

Solution: - Check container health: bash docker ps docker logs -f npm - Verify port 81 is not blocked by firewall - Check if container restarted due to volume or permission issues

Proxy Host Not Responding

Symptoms: - Clicking a domain returns 502 or times out - Internal service doesn’t appear to respond

Solution: - Confirm destination IP and port are correct - Check if upstream service is running - Enable WebSocket support if required - Check container logs for backend errors

Certificate Renewal Fails

Symptoms: - Old cert shows "Expires soon" or “Renewal failed”

Solution: - Go to SSL Certificates → manually click Renew - Check if NPM has access to issue again (DNS or port 80) - For DNS challenge, renews automatically if token is still valid

Useful Commands

docker logs -f npm
docker exec -it npm nginx -t
docker inspect npm

References