If you see the 'ERROR: Stream filter is not found' error then it means that a php component called 'convert.iconv.*' filter is not installed on your server. This component is widely available but the error may occur on custom configured servers like VPS or a dedicated server.
To get rid of this message you have to install 'convert.iconv.*' filter component to your store. It can be done by the server administrator. Some servers with a control panel may allow to enable that component on php configuration page.
There is good article explaining it can be done without php re-installation.
https://www.hackersgarage.com/iconv-php-extension-installation-without-recompiling-php.html