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Let’s Encrypt – Troubleshooting

Published by marisabel on August 24, 2025 
Details 
Could not issue a Let's Encrypt SSL/TLS certificate for [URL]. Authorization for the domain failed. Details Invalid response from https://acme-v02.api.letsencrypt.org/acme/authz....... Details: Type: urn:ietf:params:acme:error:connection Status: 400 Detail: [IPV6] Fetching [...]  Timeout during connect (likely firewall problem)

Checklist:

  1. check IPv6 on DNS : if on, remove. If off, add it.
  2. Remove HTTP → HTTPS redirection temporarily
  3. Check if ports 80 and 443 are allowed through firewall (specially 443)

LOG:

24/8/25 First issue was the #1, second issue was #3, now it was #2. We’ll see if it now stays stable.

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