First thing to check is if the relay has been configured to allow self registration.

Has the proper context been added to the relay config to allow the creation of users in the proper OU? This grants the RelayUser the rights to be able to create the user within the specified context.
If you are on 6.0.5.0 or higher then you will also need to modify /stoneware/webserv/web-inf/jspf/registrationContext.jspf to set the context.

Once configured, has the relay been restarted to activate these settings?

Has the RelayUser account been granted the User Registration role? Without this role, the RelayUser will not have the necessary rights to be able to create a user account.

Has the /stoneware/webserv/createuser.jsp been modified and changed to the same OU that the relay was configured for ? There is a section in the file that says which file to edit with a context. This explicitly tells webNetwork where to create the user's account when they run through the Registration process.

If using active directory, do you have SSL enabled for LDAP and is webNetwork configured to use SSL ?

If webNetwork is not talking to Microsoft Active Directory using SSL then passwords can note be managed.