Error al actualizar un certificado SSL: Could not issue/renew Let's Encrypt certificates

Error al actualizar un certificado SSL de Let's Encrypt: 

Could not issue/renew Let's Encrypt certificates

Could not renew Let's Encrypt certificates for dominio.com (login usuario). Please log in to Plesk and renew the certificates listed below manually.
Renewal of the following Let's Encrypt certificates has failed:

 * 'Lets Encrypt dominio.com' [days to expire: 5]
   [-] dominio.com
   [-] webmail.dominio.com

   Invalid response from https://acme-v02.api.letsencrypt.org/acme/authz/JOXABP3O7G9S81_6bzVK3QEYeevFqahCrGZEdgS5UxU.
   Details:  
   Type: urn:ietf:params:acme:error:connection
   Status: 400
   Detail: Fetching https://dominio.com/.well-known/acme-challenge/JCDJeWPkmgpW9r_vdy5cpz1ERSaEY9K5vu6Y9p5LarY : Connection refused


SOLUCIÓN:

En mi caso, el problema era por los registros DNS AAAA IPv6 que no están respondiendo. Elimine los registros AAAA y se solucionó el problema.