Unable to issue or renew Let's Encrypt certificate in Plesk for Windows: unauthorized 403 error

Alexander Davydov

Updated January 13, 2026 19:07

Plesk for Windows kb: technical ext: sslit

Applicable to:

Plesk for Windows

Symptoms

Let's Encrypt certificate could not be issued or renewed with the following error message:

Type: urn:ietf:params:acme:error:unauthorized

Status: 403

Detail: Invalid response from http://example.com/.well-known/acme-challenge/MANdx2vNFLjJ5yy7cNaV88NiQzddIDU7Gj3bpwTCllA [203.0.113.2]: "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">\r\n<html xmlns="http"

Accessing the challenge file URL from the error message results in "404 Not found" error.

Cause

SSL It! extension misconfiguration.

Resolution

Connect to the server via RDP.
Run the following command in command prompt as Administrator to disable SSL It!:

plesk ext sslit --common-challenge-dir -disable
Run the following command to enable it back again:

plesk ext sslit --common-challenge-dir -enable