On page:
www.artio.net/en/joomla-extensions/artio-joomsef
there are two links which should lead to this forum:
1. In section "Support and bug reports"
2. In section "Download and Links"
Both of them are www.artio.net/en/support-forums-2 which is some strange place which looks more or less like a forum but only with topics with "An invalid post id was requested." inside.

Hello,

Thank you for reporting this, I'll forward it to administrator to fix it.

Best regards,
ARTIO Support Team