Make sure translation is enabled in the Translatio Setup page.

Some of the content may be coming from the theme or a separate plugin. You will need to find the completed translation PO files and install them correctly. Reference here for more information:

https://developer.wordpress.org/plugins/internationalization/localization/

Or come to our Translatio online chat channel.

On CentOS/Feodra Linux system, the error is mostly due to the SE Linux setting which blocks the network connection. You can use the following command to change the SELinux setting:

# setsebool httpd_can_network_connect on