Unable to issue Let’s Encrypt certificate in Plesk: Status 400 – Timeout during connect (likely firewall problem)

Symptoms

• Unable to issue a certificate via the Let's Encrypt extension with the following error:

  Could not issue an SSL/TLS certificate for example.com
  Details
  Could not issue a Let's Encrypt SSL/TLS certificate for example.com. Authorization for the domain failed. Details
  Invalid response from https://acme-v02.api.letsencrypt.org/acme/authz-v3/321098646527. Details: Type: urn:ietf:params:acme:error:connection Status: 400 Detail: 203.0.113.2: Fetching http://example.com/.well-known/acme-challenge/kFBpRjpmUY0H8qwpYWlnmer8SbaJWTXEsv3ZuIsoCSg: Timeout during connect (likely firewall problem)

• Port 80 is opened:

  # nmap 203.0.113.2 -p80 -Pn
  ...
  PORT STATE SERVICE
  80/tcp open http

• Local Firewall is enabled on Juggernaut and/or Imunify360 extensions side.
• The domain has the A DNS record only (IPv4).

Cause

The connection is blocked on the firewall side, for example Imunify360 or Juggernaut Firewall.

Resolution

Consider disabling the Firewall on the Juggernaut and/or Imunify360 side.