Solved Certificate failed HTTP challenge check

[sekorulez]

On 2 of my servers I am unable to generate certificates using the HTTP-01 challenge. On SSL/TLS Certificate page I get this error:

Failed HTTP checks
DNS names listed here cannot get automatic certificates because an HTTP request for these names does not reach this server. It can happen if there are no DNS records for these names or DNS records point to a different server. To fix this error, make sure HTTP requests can reach this server or fix issues that prevent wildcard certificates from being used.
- test.mydomain.com

The wildcard option is disabled. It will not generate whatever I do. It does work with the test2.mydomain.com on a different server of mine. The systems are identical. The DNS setup is identical. The website are reachable, pingable. Everything is in working order.

After some investigation I tried to run the process manually to have some debug information:

/usr/local/directadmin/scripts/letsencrypt.sh request test.mydomain.com 4096
2026/09/03 13:08:43  info executing task            task=action=rewrite&domain=test.mydomain.com&value=letsencrypt
2026/09/03 13:08:43 debug DNS name skipped because of failed HTTP challenge check acme-mode=domain dnsName=test.mydomain.com domain=test.mydomain.com user=xxxxx
2026/09/03 13:08:43  info finished task             duration=41.368523ms task=action=rewrite&domain=test.mydomain.com&value=letsencrypt

I am unable to find what the error 'DNS name skipped because of failed HTTP challenge check' means. There is no information on why this message might occure.

I already updated directadmin, the lego program. Rebooted the server. Waited for 24 hours to see if dns changes where cached.

I will generate a certificate if I enable the wildcard option and connect it to the DNS server of my serviceprovider where the namesever is hosted. However I need it to work without the DNS option so we could also use it for our clients where we host subdomains for and don't have access to the DNS.

Does anybody know what the error means? Why it will work on 1 machine but not the other 2?

Sebastiaan

 

[zEitEr]

Hello,

Might be related to misconfigured IPv6, which probably exists in DNS but is missing or misconfigured in HTTP(s)

Does anybody know what the error means? Why it will work on 1 machine but not the other 2?

 

[sekorulez]

I already found out what the issue was, with the help of the directadmin team by sending in a ticket. On my /var/www/html directory I had an .htaccess file containing code to deny all access to protect roundcube en phpmyadmin to be accessed publically.

The Directadmin process use /var/www/html/.well-known/acme-challenge to write its validation files to for every domain. A redirect will make sure every domain uses that folder. But in this case the .htaccess prevented access. Therefor the file was not reable causing the error.