Thread:Project:Support desk/Missing "Create an Account" link

I have recently installed a wiki for project management uses. However, the end-users report that they cannot create an account - the link for that appears to be missing. The link in the upper-right hand corner is "Log in", not "Log in/Create an Account" as it is on other wikis. I'm not sure where to start looking for the source of error. Is this a common problem? How should I go about trying to fix the problem? The wiki is located at http://www.tinorobotics.org/wiki.