Did you just install our Software but you cannot login? In 99% of the cases it means your site does not have a SSL Certificate installed or our software (LC3, HD3, CC3 and CD3) is not configured to make use of the SSL Certificate you have.
Since the latest Cookie updates from all major browsers we had to change the login completely and to be secure we also made it mandatory to run our software under a valid SSL Certificate. This should not be a problem because SSL Certificate this days are mostly free.
Now that could be a problem when you install the software on a localhost without a SSL certificate for testing purpose. In this case please open your config.php file and find:
$cookie_secure = true;
and change to:
$cookie_secure = false;
That will give you the option to login insecure on sites without a SSL Certificate. However we strongly recommend that in a live environment you should use the original configuration with a valid SSL Certificate.