certificate CN did not match

[rs232]

I am following the guide to install plugins as per this page:
https://plugins.roundcube.net/

I did copy composer.json-dist on composer.json and added a plugin manually to this latter (not sure what I'm doing but here we go...)
Now when I go calling php composer.phar I get:

Code: [Select]

  [Composer\Downloader\TransportException]
  The "https://plugins.roundcube.net/packages.json" file could not be downloaded: Pe
  er certificate CN=`roundcube.net' did not match expected CN=`plugins.roundcube.net
  '
  Failed to enable crypto
  failed to open stream: operation failed

Not sure how to progress...

Thanks