You're using a very old application that doesn't have support anymore. I've tried to access what it seemed to the official website, but without luck since it leads to a page that displays a DNS error. This means the website is non-functional and the software is discontinued.
If you've reached the limits regarding your users, then I recommend checking the built-in Help, because that's the only thing you'll have access to. Additionally, delete the inactive ones and add others.