- Plesk for Linux
- Plesk for Windows
Domain has A record for
www.example.com, but not for
example.comis resolved to IP address that does not belong to Plesk server.
Note: This article describes the situation with DNS misconfiguration for a domain. For similar issues which do not involve DNS, refer to the following article - Let's Encrypt installation fails: Challenge marked as invalid.
Unable to install Let's Encrypt SSL. The following error is shown in Plesk UI: "404", "Timeout", "Could not connect", "400", "403":
<title>404 Not Found</title>
PLESK_ERROR: Error: Let's Encrypt SSL certificate installation failed: Challenge marked as invalid.
Could not connect to example.com
PLESK_ERROR: Error: Could not issue a Let's Encrypt SSL/TLS certificate for example.com. Authorization for the domain failed.
PLESK_ERROR: Error: Could not issue a Let's Encrypt SSL/TLS certificate for example.com. The authorization token is not available
Detail: Invalid response from http://example.com/.well-known/acme-challenge/abcdefghijklomnpqrstuvwxyz"
Incorrect DNS configuration for a domain.
Verify that domain name, e.g.
wwwprefix resolves globally. Use What's My DNS online DNS propagation checker.
If not, modify domain's DNS on a registrar side so that domain resolves to Plesk IP globally.
If domain resolves to both IPv6 and IPv4, make sure that the both IP addresses are configured in Plesk Domains > example.com > Web Hosting Access
If it is not possible to add IPv6 address in Plesk, then remove AAAA record from a global DNS for a domain;
Try to install Let's Encrypt certificate again.