Smart update check in WP Toolkit cannot be started: Smart Update could not connect to the website to fetch the sitemap.

Symptoms

• Smart update check in WP Toolkit on a Plesk server cannot be started and the following error message is displayed:

  Smart Update could not connect to the website to fetch the sitemap.

• Plesk is installed on an AWS server with public IP address set up as external IP for NAT while it is present on a network interface.
• Requests to webserver via public IP address from inside the server fail:

  # curl -vo /dev/null https://203.0.113.2
  * Rebuilt URL to: https://203.0.113.2/
  * Trying 203.0.113.2...
  * TCP_NODELAY set
  % Total % Received % Xferd Average Speed Time Time Time Current
  Dload Upload Total Spent Left Speed
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* connect to 203.0.113.2 port 443 failed: Connection refused
  * Failed to connect to 203.0.113.2 port 443: Connection refused
  * Closing connection 0
  curl: (7) Failed to connect to 203.0.113.2 port 443: Connection refused

Cause

Network misconfiguration (routing, excessively strong firewall).

Resolution

As a workaround, switch to external resolver:

1. Connect to a Plesk server via SSH.
2. Open /usr/local/psa/admin/conf/panel.ini file with preferred editor and add the following content into it:

   [ext-wp-toolkit]
   smartUpdatePreConfiguredDnsResolverEnabled=false