[Solved] Urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http

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1

I recently tried to obtain certificates and to renew certificated for 2 domains hosted on 2 different servers and receive the same error

FailedChallenges: Failed authorization procedure… (http-01): urn:acme:error:unauthorized :: The client lacks sufficient authorization :: Invalid response from http…

But on both servers files exist in .well-known/acme-challenge

If I try to access them in browser, I succeed.
DNS records for domains are quite old, dig resolves them.

What is more - there is nothing in nginx access and error logs except my own IP, seems that letsencrypt did not queried my domains at all.

3 months ago everything was fine with these servers and domains.

2

After digging into logs and reading some forum topics - it seems the problem was with challenge validation over IPv6.

Issue resolved.

3

How did you resolve the ipv6 issue?

4

As I had no access to make server support IPv6 properly, the only way was
to remove AAAA records from DNS.