Unable to install Let’s Encrypt certificate for domain in Plesk: Could not obtain directory: cURL error 77

Symptoms

• The following error occurs in an attempt to install Let’s Encrypt certificate:

  PLESK_ERROR: Could not obtain directory: cURL error 77: (see http://curl.haxx.se/libcurl/c/libcurl-errors.html))

• The following text is displayed upon accessing http://acme-v01.api.letsencrypt.org/ in web browser:

  An error occurred while processing your request.
  Reference #97.850af748.1526081586.5cab750

• The following error can found in Plesk panel.log with debug enabled:

  [2018-03-21 02:21:23] INFO [extension/letsencrypt] Begin validation for domains: example.com, www.example.com...
  [2018-03-21 02:21:23] NOTICE [extension/letsencrypt] >>>>>>>>
  GET /directory HTTP/1.1
  User-Agent: Plesk/12.5.30 letsencrypt/2.5.3-354 GuzzleHttp/6.2.1 curl/7.29.0 PHP/5.6.14
  Host: acme-v01.api.letsencrypt.org
  <<<<<<<< --------
  cURL error 77: (see http://curl.haxx.se/libcurl/c/libcurl-errors.html)

Cause

Let’s Encrypt server is currently under maintenance.

Resolution

The issue will be resolved automatically.
Let’s Encrypt services status can be found via the following link: https://letsencrypt.status.io/.
If the issue still persists after http://acme-v01.api.letsencrypt.org/ starts providing a valid response, connect to the server via SSH and restart the sw-engine and sw-cp-server processes:

# service sw-engine restart
# service sw-cp-server restart