Simple Press User Registration Issues…Please help

I have installed the simple press forum plug-in. I love it and it works great except I can’t figure 1 thing out:

When users go to register for the forum, they are taken to this page:
http://www.domainname.com/wp-login.php?

Once they fill out the form, they are told an email will be sent to them with their password.
No one is getting this email. And this is the problem.

Please tell me step by step instructions on how to fix this issue.

I also have contact forms on my site and they are working fine.
I am using Atahualpa theme.

Thank you