WordPress plugin installation/update failed on Plesk server: An unexpected error occurred

Symptoms

• WordPress Plugin could not be updated or installed in WordPress admin interface. The following error is shown on the Add New page and on Installed Plugins when viewing the plugin’s details:

  Warning: An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums. (WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.) in C:Inetpubvhostsexample.comwp-adminincludesplugin-install.php on line 169

• The domain is using PHP 5.3.

Cause

Internal PHP engine error related to cURL routines.

Resolution

1. Log into Plesk.
2. In Domains > example.com > PHP Settings select PHP version 5.6 or higher.