Error «query: Couldn't connect to server» when opening phpMyAdmin

Symptoms

When switching from the control panel to phpMyAdmin, the error «Type: 'rpc' Object: 'query' Value: 'query: Couldn't connect to server'» appears.

Causes

The Nginx web server is configured incorrectly.

Solution

In the Web server settings section, disable and then re-enable the Enable access to external applications over SSL option to recreate the file at /etc/nginx/ssl_cert_servers/manager.conf.